What are logic errors?

What are logic errors? : A logic error is an error in a program’s source code that gives way to unanticipated and erroneous behavior A logic error is classified as a type of runtime error that can result in a program producing an incorrect output It can also cause the program to crash when running

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Language usage mistakes include syntax errors . Missing a comma , a quotation mark, or spelling a word incorrectly are all examples of syntax errors. Syntax mistakes will be noted by MATLAB and an error message will be displayed. The final quote is absent from the character vector for example:

>> mystr = ‘how are you;

mystr = ‘how are you;

 

Error: Character vector is not terminated properly.

If this type of error is typed in a script or function using the Editor, the Editor will flag it

Making a typographical error in a variable name is another frequent error that MATLAB will detect. As shown in the following example, more recent versions of MATLAB should be able to fix this for you.

>> value = 5;

>> newvalue = valu + 3;

Unrecognized function or variable ‘valu’.

Did you mean:

>> newvalue = value + 3;

Runtime errors, also known as execution-time errors, are discovered while a script or function is running. An example of a runtime error with the majority of programming languages is attempting to divide by zero. However, this will return the constant Inf in MATLAB. Another illustration would be trying to refer to a nonexistent element in an array.

runtimeEx.m

% This script shows an execution-time error

vec = 3:5;

for i = 1:4

 disp(vec(i))

end

The previous script initializes a vector with three elements, but then attempts to refer to a fourth. Runningit prints the three elements in the vector, and then an error message is generated when it attempts to refer to the fourth element.

Note

The error’s cause is explained by MATLAB, and the script’s line number where the error occurred is also provided.

>> runtimeEx

 3

 4

 5

Index exceeds array bounds.

Error in runtimeEx (line 6)

 disp(vec(i))

Since they don’t produce an error message, logical errors are more challenging to find. The difference between a logical error and a programming language error is that the former is a mistake in the programmer’s reasoning. A logical mistake would be dividing by two. To convert inches to centimeters, multiply by 54 as opposed to dividing. Even though it might not be obvious, the results printed or returned would be inaccurate.

Every program should be reliable and, whenever possible, foresee potential errors and take precautions to avoid them. For instance, whenever a program receives input, it should error-check the input to ensure that the values are within the proper range. Additionally, any denominator should be checked to make sure it is not zero before being divided.

Despite the best precautions, there are bound to be errors in programs

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Errors and Pitfalls

Brian H. Hahn, Daniel T. Valentine, inEssential MATLAB for Engineers and Scientists (Sixth Edition), 2017

11.1 Syntax errors

Syntax errors are typing errors in MATLAB statements (e.g.,plog instead of plot). They are the most frequent type of error, and are fatal: MATLAB stops execution and displays an error message. As MATLAB evolves from one version to the next, error messages improve. Try the following examples to examine the latest error messages:

     2*(1+3

     disp([‘the answer is ‘ num2str(2)]

There are many different syntax mistakes that can happen—you most likely have run into a few yourself. You’ll get better at recognizing your errors as you gain experience.

The function lasterr returns the last error message generated.

11.1.1 Incompatible vector sizes

Consider the following statements:

x = 0:pi/20:3*pi;y = sin(x);x = 0:pi/40:3*pi;plot(x,y)

You’ll get the error message

Error using ==> plotVectors must be the same lengths.

because you forgot to recalculate y after reducing the xincrements. whos reveals the problem:

x         1×121          …y         1×61           …

11.1.2 Name hiding

Remember that a workspace variable hides an identical script or function. Clearing the offending variable from the workspace is the only way to gain access to such a script or function.

Furthermore, a MATLAB function hides a script of the same name, e.g., create a script called why.m that displays some junk message, and then type why at the command line.

If you areworried that a variable or script which you are thinking of creating, say blob, may be a MATLAB function, try help blob first.

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PIC16 C Applications and Systems

Martin P. Bates, inProgramming 8-bit PIC Microcontrollers in C, 2008

Application Debugging and Testing

The application program is tested and debugged in several stages. The maintypes of errors and the tools for detecting them are outlined next.

Syntax errors are mistakes in the source code, such as spelling and punctuation errors, incorrect labels, and so on, which cause an error message to be generated by the compiler. These appear in a separate error window, with the error type and line number indicated so that it can be corrected in the edit window.

After the program has been successfully compiled, it can be tested to see if it operates correctly on the target hardware in order to find any logical errors. However, it is preferable to test it out in software simulation mode first because it makes it quicker and simpler to find programming errors. Here, MPSIM and Proteus VSM are the two simulation techniques available.

MPSIM is the simulator provided with MPLAB. It allows the programsource code to be run, stopped and stepped, and breakpoints set. The registers and source variables may be inspected at each step. When debugging C programs, breakpoints are the most useful, while stepping is more useful in assembly language. The program sequence and variable values are monitored and errors identified when the results obtained do not agree with those expected. Error information is provided principally in tabular form.

By comparison, the Proteus VSM debugging environment has significant advantages The animated schematic gives a much more immediate indication of the overall program function Interactive input and output devices operate in real or simulated time The source code and breakpoints can be displayed

In addition, if the VSM viewer is run from within MPLAB, the progress of the program can also be monitored simultaneously in MPSIM Therefore, the more detailed debugging tools in MPSIM can be run alongside VSM and the most appropriate selected for any debugging task The simulated hardware design is thus tested in conjunction with the MCU firmware (cosimulation), allowing circuit modifications at an early stage and hardware-software interaction to be studied on screen When the program is eventually downloaded to the real hardware, it is now far more likely that it will work the first time

The VSM Viewer is invoked from the debug tools menu in MPLAB, and the program is attached and tested. However, if circuit modifications are needed, VSM must be opened separately to run alongside MPLAB, so that the full set of ISIS schematic edit tools and component models are available. VSM still accesses the same COF file, so both software and hardware changes can be tested. More details on interactive debugging are given in Appendices A, B, andCAppendix AAppendix BAppendix C.

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Program Development and Testing

Andrew P. King, Paul Aljabar, inMATLAB Programming for Biomedical Engineers and Scientists, 2017

4.4 Debugging a Function

The basics of the MATLAB debugger were described in Section 1.12. Here, we consider some of the types of errors that the debugger can be used to help identify and fix.

When writing a program or function that is non-trivial, the chances of it working perfectly first time are quite low, even for a skilled MATLAB user Debugging tools are there to help identify why a program does not work correctly or asexpected

When debugging, we need to work systematically and run our program with various sets of test data to find errors and correct them when we find them. If we work incrementally as we did in Example 4.1 above, then the repeated nature of the testing allows errors to be caught earlier, which reduces the chance of later errors occurring or minimizes their severity.

A function or program may contain one of three different types of errors:

Syntax errors.

Run-time errors.

Logic errors.

A programming language’s grammar is referred to as its syntax. The syntax of a language refers to the specific set of rules that govern how commands can be expressed in that language.

When a line in a MATLAB function contains a syntax error, the built-in Code Analyzer (see Section 1.12.2) should highlight in red the corresponding line of code. Hovering the mouse over the line should result in a message being displayed to the user that describes what MATLAB has decided is the particular syntax error in the line. In other words, MATLAB can detect an error with the script or function before itis run.

Example 4.2 A syntax error

If the following code is inserted into a script, say my_ script. m, then the line containing the using the editor.

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a statement with a syntax error should be highlighted in red.

This is so because MATLAB’s syntax requirements call for a closing.

statement foreach

statement.

O4.C, O4.D

If we fail to notice this error and attempt to run the script from the command window, we will get an error when MATLAB reaches the relevant part of the codeand a more dramatic message will be displayed:

   >> my_script

Clicking on the part of the error report with the line number will take us directly to the corresponding place in the script file so that we can figure out how tocorrect the error. In this case, adding an statement after the call should be enough.

Activity4.2

Type the code from the previous example into a script Confirm that the Code Analyzer highlights the error Fix the error and confirm that the highlighting disappears

O4.C, O4.D

Example 4.3 Another syntax error

The following code contains asyntax error. The MATLAB code analyzer should highlight it in red. The code begins by generating a single random number between 1 and 10 and then it seeks to decide if the random number equals three or not, adjusting its output in each case.

O4.C

Activity 4.3

Enter the script’s code using the syntax from the previous example. Confirm that the error is highlighted by the Code Analyzer. Correct the problem, then make sure the highlighting goes away.

O4.C, O4.D

The reason for this syntax erroris that the

sign used in the statement is an assignment operator and should not be used to test for equality. The correct symbol to usehere is the comparison operator which is in MATLAB, i.e. two equals signs, not one (see Example 2.2). This is also the case in quite a few other languages and it is very common to mix up these operators.

Example 4.4 A run-timeerror

While we are editing the code, MATLAB cannot detect some errors; these errors can only be detected after the code has been run. This is due to the fact that a particular set of commands must be executed in order to create the error’s circumstances. Take a look at the code in a script called someScript, as shown below. m. Three numerical sequences are intended to be produced and then assigned to array variables.

,

and

Then, it attempts to determine the sums of each of these sequences (line numbers are shown here to aid in the description).

In this case, there are no syntax errors but running the script at the command window leads to a run-time error as follows:

O4.C

Activity 4.4

Type the code from the previous example into a script Run the script from the command window to reproduce the error

O4.C

The problem with the code in Example 4.4 is related to the choice of variable names. The sums of the arrays

and have been given sensible names ( and ). The sum of the array variable has been stored in a variable called . This is a problem because the local script has used the name of a built-in MATLAB function as a name for a local variable.

Using the name of a built-in function for a variable that we use locally is called shadowing. We can check if a name is already used by MATLAB or inthe workspace using the

command. In this case, we can trivially check

The name is indicated by the return value of 5.

exists and is connected to a function (as opposed, say, to a file). Type.

, where you can find more information. We can check a more logical name by doing as follows:.

The value of 0 returned indicates that the name

is not being used and we can safely use it inour code

Returning to the code in Example 4.4, when the execution reaches line 13, the programmer’s intention was to use the built-in MATLAB function called

, but this now refers to a local variable that contains a single number. The use of the brackets in line 13 isnow interpreted as a request for an element or elements taken from an array called . The elements requested are at the indices specified by another variable, .That is, the indices requested start at 3 and go up to 30 in steps of 3. The problem however, is the variable called is just a single scalar value, i.e. it as an array of length one. It is not possible to obtain an element from it at index 3 or higher. This is the reason for the code crashing at run-time.

This example demonstrates why it is crucial to avoid giving names to variables that are already used to refer to built-in functions in addition to serving as an example of a run-time error. Be careful because MATLAB won’t object if you do this.

Example 4.5 A run-time error

Here is some more code that gives a run-time error:

In this case, when the code is run, the following output is given

   >> someScript

O4.C

Activity 4.5

Type the code from Example 4.5 into a script. Run the script from the command window to reproduce the error. Can you see why this erroroccurs?

O4.C

The script in Example 4.5 calls

at the start. This means that even if the workspace contained a global variable called before calling the script, then it would have been cleared and would no longer be available. Hence, the request to calculate will always fail as there is no variable called. This would need to be defined before the point where the function is called to make the code work (but after the ).

Activity 4.6

Fix the code from Example 4.5 by introducing an appropriate local variable and assigning a value to it. Run the script to check it works.

O4.D

Logic Errors

Logic errors can be some of the hardest to find, and identifying them often requires using the debugger to carry out careful line-by-line inspection of the code as it is running. This is because no error is reported by MATLAB and the Code Analyzer does not highlight anything either. However, when the code is run, an incorrect output or behavior results and MATLAB will generally notprovide a clue as to why this happened.

Example 4.6 A logic error

In this example, the following code attempts to show that sin⁡θ=12 when θ=30∘:

When we actually run the code, we get the following output with no error reported:

  >> someScript  These should be equal: -0.99 and 0.50

O4.C

This shows two numbers that are clearly not equal so what has gone wrong?

Activity 4.7

Typethe code from Example 4.6 into a script and run it to reproduce the same output.

O4.C, O4.D

Can you see why the output is incorrect? Place a breakpoint in the code and run the script again Check the values of the variables to see if there is a clue

To track down the reason for the behavior in Example 4.6 we need to carry out some further investigation. Inthe command window we can look at the help on the

function which we might suspect of being broken:

  >> help sin   sin    Sine of argument in radians.      sin(X) is the sine of the elements of X.

This demonstrates that we should provide the built-in MATLAB trigonometric function with an argument in radians since that is what it expects. The sine of 30 radians, not degrees, as calculated by the function when used as described above, produced the right result. That is, our expectations of the function and what it was intended to do were at odds. This error can be quickly fixed in a number of ways, such as by replacing with wherewe have used the built-in MATLAB constant.

Activity 4.8

Fix the code in Example 4.6 and confirm that sin⁡30∘ does indeed equal 1/2!

O4.C, O4.D

Because no error message is given, logic errors can be difficult to detect. Sometimes we might not even notice that the program or function is behaving wrongly. Even when we suspect a logic error exists, by noticing something incorrect in the program’s behavior,it can still be difficult to pinpoint where the error is. There is no error message helpfully pointing us to a specific line in the code, as in the case of syntax errors. Worse still, the error will not necessarily be restricted to just one line – it can arise from the way different sections of code interact.

The error in the previous example was due to the intention to use degrees where radians should have been used instead. This is only noticed by observing the actual values of the output and seeing that the numeric value is not correct; in other words, by careful inspection of the output.

One way to identify logic errors in a function is to use the MATLAB interactive debugger to step through the function line-by-line, perhaps with a calculator or pencil and paper to hand (see Section 1.12).

Another method is to copy and paste each line of code into the command window. Then, after each line has been executed, check the outcome to ensure that it is correct.

It can also be helpful to use the or commands to place numerous statements in the code that show output and the values of the most important variables. Before and after crucial code sections, for example, variable values can be shown. g. calls to other processes or crucial control elements like clauses and loops. The extra output statements should be removed once we have verified and are confident that the function or program is operating properly.

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PIC Program Development

Martin Bates, in PIC Microcontrollers (Third Edition), 2011

4.6.1 Syntax Errors

If there areany syntax errors in the source code, such as spelling, layout, punctuation or failure to define labels properly, error messages will be generated by the assembler. These will be displayed in a separate window, indicating the type of error and line number. The messages and line numbers must be noted, or the error file, BIN4.ERR, printed out then the necessary changes made to the source code. The error is sometimes on a previous line to the one indicated, and sometimes a single errorcan generate more than one message. Warnings and information messages can usually be ignored, and can be disabled. There are more details about error messages in Chapter 9.

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You may receive the following messages:

 Warning[224] C:\MPLAB\BOOKPRGS\BIN4.ASM 65 : Use of this instruction is not recommended.

 Message[305]C:\MPLAB\BOOKPRGS\BIN4.ASM 81 : Using default destination of 1 (file).

The first warning is caused by the special instruction TRIS, which is not part of the main instruction set. It is a simple way of initializing the port, and there is an alternative method using register bank selection, which is preferred in real applications. This will be introduced later.

The message about the default destination is a result of the programs’ streamlined syntax, which prevents the file register from being explicitly specified as the destination in instructions where the outcome can be put either in the file register or the working register. We are using this as an opportunity to streamline the source code since the assembler by default treats the file register as the destination.

When all errors have been eliminated and the program has been successfully assembled, the machinecode can be inspected by selecting ‘View’, ‘Program Memory’. Note that the source code labels are not reproduced, as the program code has been ‘disassembled’ (recreated) from the machine code. That is, the hex file has been converted back to mnemonic form so that it can be checked against the original.

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MATLAB® Debugging, Profiling, and Code Indentation

MuntherGdeisat, Francis Lilley, in Matlab by Example, 2013

Lesson 8.1 MATLAB® Debugging

Objectives

To learn the differences between syntaxerrors and runtime errors.

To learn how to debug MATLAB script files.

To learn how to use the Breakpoint tool to debug MATLAB code.

To learn how to run one line of a program using the Step tool.

Topics

8.1.1

Syntax and Runtime Errors

8.1.1.1

Syntax Errors

8.1.1.2

Runtime Errors

8.1.2

Debugging MATLAB® Code

8.1.2.1

Setting Up a Breakpoint

8.1.2.2

Stepping Through theProgram

8.1.1 Syntax and Runtime Errors

There are two types of errors that appear in MATLAB expressions: syntax errors and runtime errors. Together, we generically refer to these errors as being bugs in the MATLAB code. The debugging process is the procedure of finding these bugs and fixing them.

8.1.1.1 Syntax Errors

Let us start with the first error type, which is the syntax error. These errors mainly occur as a result of the misspelling of variable or function names or from missing quotes or parentheses (or the accidental extraneous typing of an additional one of these). Examples of such errors are given below:

>>x=x*(1+2*x));%extraparenthesis>>x=1;x=x(x+1)%Themultiplicationsignismissing>>y=‘hello%missingquote>>z=1;disp(Z);%MATLABiscasesensitive,soZisnotthe%sameasz.

Note that you can type more than one MATLAB command in a single line, but these commands should be separated by a comma(,) or a semicolon (;).

When you type a MATLAB command in the Command Window, MATLAB checks for syntax errors before running the command. If the command passes the syntax error check, then MATLAB executes this command; otherwise, MATLAB displays a message reporting that there is a syntax error and that it should be fixed before attempting to run this command again. Also, MATLAB may give you some information thathelps in identifying and fixing this error.

Suppose that you attempt to run a MATLAB script file that contains syntax errors. MATLAB does not run this file and responds by reporting that the file contains syntax errors. It rather helpfully provides you with the line number that contains the first syntax error that it has found in the file, and it also advises you about how to fix this error.

8.1.1.2Runtime Errors

Runtime errors are found by MATLAB during the execution of a program, and they are generally more difficult to fix than simple syntax errors. The ability to fix runtime errors is something that improves with experience and is best learned by way of an example.

Write a MATLAB program that computes a vector’s absolute values for a test run. The integer values from 10 to 10 make up the input vector in this example. As a result, all positive input values in the range of 10 to 10 should remain unchanged (along with zero), and all negative input values will lose their negative signs to reveal only their magnitude, as in the case of the value 3 becoming 3. the input vector is, that is.

−10−9−8−7−6−5−4−3−2−1012345678910

which should produce an output vector as follows:

10987654321012345678910

Launch the MATLAB Editor. Type the code below into the Editor window. Save the script file with the name absolute.m.

It is advisable to start any MATLAB script file with the commands clear; clc;. These two respective commands delete any unwanted variables in the MATLAB memory and also clear theCommand Window. The command close all closes all figures in MATLAB.

clear; clc; close all

x = −10:10;

for k = 0:length(x)

 if (x(k) > 0)

  x(k) = −x(k);

 end

end

disp(x)

Activate the program. There are mistakes in the code, according to MATLAB. The error is reported as follows by MATLAB:.

??? Attempted to access x(0); index must be a positive integer or logical.

Error in ==> absolute at 4

 if (x(k) > 0)

MATLAB starts indexing any vector with the index 1. This is unlike several other programming languages, such as C, which start the indexing process with index zero. So, we have identified this runtime mistake, which must be fixed by changing the index in the third line (beginning for k =) from the current value of 0 to a value of 1, as shown in the following code segment:

clear; clc;

x = -10:10;

for k = 1:length(x)

 if (x(k) > 0)

  x(k) = -x(k);

 end

end

disp(x)

Rerun the program after fixing the bug. The results MATLAB produces are not what was anticipated, as can be seen in the following figure. Although they ought to be, none of the numbers that are generated are positive. Therefore, we must fix this bug. and we’ll locate the bug’s exact location and characterize it using MATLAB’s debugging features.

8.1.2 Debugging MATLAB Code

8.1.2.1 Setting Up a Breakpoint

MATLAB has a feature that allows the user to control the execution of an M-file program. This feature helps intracking down the bugs and fixing them. For example, you can introduce a Breakpoint in a program, and the execution of the code temporarily stops at this Breakpoint. Then you can check the values of the MATLAB variables at this point and try to figure out the cause of the bug.

To debug your program, go to the Editor window. Using the mouse, left-click in the space between the column of line numbers and the code itself (where there isa column of dashes “–”) and place the Breakpoint in the position pointed at by the arrow in the following diagram. A red circle then appears as shown. This can be toggled on and off by clicking again in the same place. If you practice toggling this here, make sure you leave the Breakpoint set to ON, with the red dot showing as in the following figure.

Go to the Menu→Debug→Run absolute.m.

Note that as a result ofdoing this, the MATLAB Command Prompt changes to

k>>

which informs you that MATLAB is now running in debug mode

MATLABstarts executing the program and stops at line 1.

8.1.2.2 Stepping Through the Program

To direct MATLAB to run the command in line 1, click on the Step icon (pointed at by the arrow inthe following figure).

MATLAB executes the first line before moving on to line 2.

An alternative way to step through the program is by pressing the F10 key on the keyboard. Press F10 to make MATLAB run line 2 of the code.

Move the mouse and place the cursor directly over the variable x. A yellow box pops up and tells you the values of x.

Alternatively, you can get the values of this vector variable by double-clicking on x in the Workspace window.

Press F10 to run line 3. Using the mouse, highlight the expression (x(k) > 0). Place the mouse cursor over the highlighted area and right-click. Choose Copy from the Context Menu.

In the Command Window, right-click the mouse and choose Paste. Then press Enter on the keyboard. MATLAB evaluates the expression and informs us that it has a value of 0. In this manner you can determine the value of any expression or variable.

The value of the first element in the variable x is −10. Press F10. The code steps to line 7. It should have entered the if statement and gone to line 5 to change the sign of the first element, but it did not. Instead it went toline 7. By noting this, we can discover that there is a programming error in the condition for the if statement. The greater than character “>” should be changed to the less than character “<”.

Fix this bug bychanging the character “>” to “<”. Then go to the Menu→Debug→Exit Debug Mode. This terminates the debugger in MATLAB.

The bug is now fixed. Remove the Breakpoint. This can be carried out by usingthe mouse. Left-click in the space between the code and the line number 1 (pointed at by the arrow in the figure) to toggle the Breakpoint to off. The red dot disappears.

Run the code by clicking the Run icon. MATLAB executesthe program and produces the correct output.

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Errors, Good Programming Practices, and Debugging

Alexandre M. Bayen, Timmy Siauw, inAn Introduction to MATLAB® Programming and Numerical Methods for Engineers, 2015

9.1 Error Types

There are three basic typesof errors that programmers need to be concerned about: syntax errors, runtime errors, and logical errors. Syntax is the set of rules that govern a language. In written and spoken language, rules can be bent or broken to accommodate the speaker or writer. However, in a programming language the rules are completely rigid. A syntax error occurs when the programmer writes an instruction using incorrect syntax. Forexample, 1 = x is not legal in the MATLAB programming language because numbers cannot be assigned as variables. If the programmer tries to execute one of these instructions or any other syntactically incorrect statement, MATLAB will return an error to the programmer in the form of a red message with the line where the error occurred and the probable cause. This is commonly called throwing an error.

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EXAMPLE:

Syntax error examples.

Syntax errors are usually easily detectable, easily found, and easily fixed. Runtime errors are much more difficult to find. Runtime errors are only detectable when a program is run.For example, concatenation is legal in MATLAB syntax, but if you try to concatenate arrays of incorrect dimensions, then MATLAB will not be able to carry out your instruction, and an error will be produced.

EXAMPLE:

Runtime error examples.

MATLAB will stop and let you know where the issue is, making the majority of runtime errors simple to locate. A function is typically run several times after it has been programmed by an experienced programmer so that any errors can be caught and corrected.

One ofthe most difficult kinds of runtime errors to find is called a logic error. A logic error does not throw an error, but is an error because the output you get is not the solution you expect. For example, consider the following erroneous implementation of the factorial function.

EXAMPLE:

Erroneous factorial function.

This function will not produce an error for any input that is valid for acorrectly implemented factorial function. However, if you try using myBadFactorial at the command window, you will find that the answer is always 0 because out is initialized to 0 instead of 1. Therefore, the line out = 0 is a logic error. It does not produce an error by MATLAB, but it leads to an incorrect computation of factorial.

When programs get longer and more complex, errors are notoriously difficult to find even though they seem unlikely to happen or at least as simple to spot as other types of errors. You are forced to carefully go through every line of your code to find the issue when logic errors occur. It’s critical to avoid making any assumptions in these situations and to fully understand how MATLAB will react to each command you issue. You can also use MATLAB’s debugger, which will be discussed in the final section of this chapter.

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Design Automation of FPGAs

Peter Wilson, in Design Recipes for FPGAs(Second Edition), 2016

5.2.1 Simulators

Simulators are a key aspect of the design of FPGAs. They are how we understand the behavior of our designs, check the results are correct, identify syntax errors and even check postsynthesis functionality to ensure that the designs will operate as designed when deployed in a real device. There are a number of simulatorsavailable (all the main design automation vendors provide software) and the FPGA vendors also will supply a simulator usually wrapped up with the design flow software for their own devices. This altruistic approach is very useful in learning to use FPGAs as, while they are clearly going to be targeted with libraries at the vendor’s devices, the basic simulators tend to be fully featured enough to be very useful for most circumstances. One of the most prevalent simulators is theModelSim® from Mentor Graphics, which is generally wrapped in with the Altera and Xilinx design software kits and is very commonly used in universities for teaching purposes. It is a general-purpose simulator which can cater for VHDL, Verilog, SystemVerilog and a mixture of all these languages in a general simulation framework. A screen shot of ModelSim in use is shown in Figure 5.1 and it shows the compilation window and a waveform viewer. There are other ways touse the tool including a transcript window and variable lists rather than waveforms—useful in seeing transitions or events.

Figure 5.1. ModelSimsimulator user interface.

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Program Debugging

Martin Bates, in PIC Microcontrollers (Third Edition),2011

Publisher Summary

This chapter describes program debugging which involves the removal of errors from PIC programs. The rules in programming language are very strict, because the source code must be converted into machine code without any ambiguity. Syntax errors are mistakes in the source code, such as misspelling of an instruction mnemonic or failure to declare a label before using it in the program. Thiserrors are detected by the MPLAB assembler (MPASM), resulting in error messages being generated and displayed in a separate window. The source code is color coded in recent versions of MPLAB to highlight correct syntax and errors. If a syntax error is detected, the correct use of the instruction set and assembler directives must be checked against the programming rules. Once a program has been assembled without any syntax errors, it may still not function correctly as logical errors may bepresent which prevent correct operation. The software simulator (MPSIM) can be used to detect and correct these errors prior to downloading to the chip.

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URL: https://www.sciencedirect.com/science/article/pii/B9780080969114100096

Language Reference Guide

John Iovine, in PIC Projects forNon-Programmers, 2012

C Code

Enter any C code you wish to include in the flowchart. The C code is not checked by Flowcode but is passed straight to the C compiler when the flowchart is compiled. It is important to verify that the C code entered is correct, as syntax errors will cause the compilation of the whole flowchart tofail.

To access Flowcode variables, macro functions and connection points, it is necessary to color the variable in your C code with the prefixes FCV_, FCM_ and FCC_MacroName_ respectively For example, to use a Flowcode variable called DELAY in your C code, you must refer to it using FCV_DELAY Note that all Flowcode defined variables are upper case To call a Flowcode macro called TEST in your C code, you must call FCM_TEST(); Note that allFlowcode macro names are upper case

Your C code needs to go to FCC_TEST_A; in order to access the connection point A, which is defined in the Flowcode macro TEST. The prefix FCC_Main_ is used to identify connection points defined in the main flowchart of a flowcode file. Use Ctrl Tab to enter a tab character in the C code field.

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URL: https://www.sciencedirect.com/science/article/pii/B9781856176033000063


What are the logical errors provide example? : A logical error is a flaw in the programmer’s logic; it is not a flaw in the programming language. Dividing by two is an illustration of a logical mistake. To convert inches to centimeters, divide by 54 rather than multiplying. It might not be obvious that the results printed or returned are incorrect.
What are the types of logical error? : These are some examples of error types: syntax error. logical or semantic error. Runtime error
What is logical error and syntax error? : Difference Between a Syntax Error and a Logical Error A Syntax Error is a Mistake in the Syntax of a Sequence of Characters or Tokens Written in a Specific Programming Language. A logical error is a programming error that makes a program behave incorrectly but does not result in an abnormal program termination.

Additional Question — What are logic errors?

What are the three types of errors?

Human, random, and systematic errors are the three categories of errors. Systematic Error. The sources of systematic errors are known. Random Error Unexpected changes lead to random errors. Error by people. Human error is a polite way of saying carelessness.

What are the 3 types of error in programming?

There are three different types of errors that can happen when developing programs: syntax errors. errors in logic. runtime mistakes.

What is logical error in C with example?

When we expect something, but the outcome is something different, we call that a logical error. Let’s say we want the sum of two numbers but the output is the multiplication of two numbers; this is referred to as a logical error. Line-by-line debugging can be used to find it.

What is the difference between syntax error and semantic error?

While a semantic error is flawed logic that results in the incorrect behavior when applied, a syntax error is an incorrect construction of the source code.

What is the difference between logical error and runtime error?

Definition. A logical error is an error in a program that causes it to run incorrectly but not abnormally, as opposed to a runtime error, which occurs while a computer program is actually running. The main distinction between a runtime error and a logical error is this.

What is logical error class 11?

We make logical programming errors, which lead to logical errors. The program cannot be built or run. The program is built and run, but it doesn’t produce what is expected. The compiler recognizes syntactic errors. The developers of the program must identify and fix any logical errors.

What are the types of errors in computer?

The top 7 programming errors are listed below: Runtime errors. Defects in logic. coding mistakes. incorrect syntax. interface mistakes. Misuse of resources error in computation.

What are the types of errors in computer class 11?

Compile-time errors, run-time errors, and logical errors are the three main categories of errors.

What is logical error Python Class 11?

Our programming errors in logic cause logical errors to happen. The compilation and execution of the program fail. The program is built and run, but the intended result is not produced. The compiler detects syntax errors. The program’s developers must identify and fix logical mistakes.

What is logic error in Python?

Logical errors These happen when a program runs normally but generates an incorrect outcome. The logic of the program was flawed, which resulted in the error. Because there was no syntax or runtime error, you won’t receive an error message.

What are the three types of error in Python?

Syntax errors, exceptions, and logical errors are the main three types of Python errors that can be distinguished.

Dannie Jarrod

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