C Programming Interview Questions Answers Part-II

This post is about C Programming Interview Questions Answers Part-II. I hope you have been through Part-I, if not then I recommend you please check. This post will find helpful for preparing any job interview or even for academics. The post design in such a way to understand nature of questions one may encounter during interview of subject related to C Programming.

1) What are logical errors and how does it differ from syntax errors?

Program that contains logical errors tend to pass the compilation process, but the resulting output may not be the expected one. This happens when a wrong formula was inserted into the code, or a wrong sequence of commands was performed. Syntax errors, on the other hand, deal with incorrect commands that are misspelled or not recognized by the compiler.

2) What could possibly be the problem if a valid function name such as tolower() is being reported by the C compiler as undefined?

The most probable reason behind this error is that the header file for that function was not indicated at the top of the program. Header files contain the definition and prototype for functions and commands used in a C program. In the case of “tolower()”, the code “#include <ctype.h>” must be present at the beginning of the program.

3) What is debugging?

Debugging is the process of identifying errors within a program. During program compilation, errors that are found will stop the program from executing completely. At this state, the programmer would look into the possible portions where the error occurred. Debugging ensures the removal of errors, and plays an important role in ensuring that the expected program output is met.

4) What does the && and || operator do in a program code?

The && is also referred to as AND operator. When using this operator, all conditions specified must be TRUE before the next action can be performed. If you have 10 conditions and all but 1 fails to evaluate as TRUE, the entire condition statement is already evaluated as FALSE.

The || is also known as the OR operator in C programming. When using || to evaluate logical conditions, any condition that evaluates to TRUE will render the entire condition statement as TRUE.

5) How do you generate random numbers in C?

Random numbers are generated in C using the rand() command. For example: anyNum = rand() will generate any integer number beginning from 0, assuming that anyNum is a variable of type integer.

6) In C programming, what command or code can be used to determine if a number of odd or even?

There is no single command or function in C that can check if a number is odd or even. However, this can be accomplished by dividing that number by 2, then checking the remainder. If the remainder is 0, then that number is even, otherwise, it is odd. You can write it in code as:

if (num % 2 == 0)
 printf("EVEN");
else
 printf("ODD");

7) What are the different types of control structures in programming?

There are 3 main control structures in programming: Sequence, Selection and Repetition. Sequential control follows a top to bottom flow in executing a program, such that step 1 is first perform, followed by step 2, all the way until the last step is performed. Selection deals with conditional statements, which mean codes are executed depending on the evaluation of conditions as being TRUE or FALSE. This also means that not all codes may be executed, and there are alternative flows within. Repetitions are also known as loop structures, and will repeat one or two program statements set by a counter.

8) Can the “if” function be used in comparing strings?

No. “if” command can only be used to compare numerical values and single character values. For comparing string values, there is another function called “strcmp” that deals specifically with strings.

9) What are preprocessor directives?

Preprocessor directives are placed at the beginning of every C program. This is where library files are specified, which would depend on what functions are to be used in the program. Another use of preprocessor directives is the declaration of constants. Preprocessor directives begin with the # symbol.

10) What will be the outcome of the following conditional statement if the value of variable s is 10?

s >=10 && s < 25 && s!=12

The outcome will be TRUE. Since the value of s is 10, s >= 10 evaluates to TRUE because s is not greater than 10 but is still equal to 10. s< 25 is also TRUE since 10 is less than 25. Just the same, s!=12, which means s is not equal to 12, evaluates to TRUE. The && is the AND operator, and follows the rule that if all individual conditions are TRUE, the entire statement is TRUE.

11) Describe the order of precedence with regards to operators in C.

Order of precedence determines which operation must first take place in an operation statement or conditional statement. On the top most level of precedence are the unary operators !, +, – and &. It is followed by the regular mathematical operators (*, / and modulus % first, followed by + and –). Next in line are the relational operators <, <=, >= and >. This is then followed by the two equality operators == and !=. The logical operators && and || are next evaluated. On the last level is the assignment operator =.

12) What is wrong with this statement? myName = “Robin”;

You cannot use the = sign to assign values to a string variable. Instead, use the strcpy function. The correct statement would be: strcpy(myName, “Robin”);

13) How do you determine the length of a string value that was stored in a variable?

To get the length of a string value, use the function strlen(). For example, if you have a variable named FullName, you can get the length of the stored string value by using this statement: I = strlen(FullName); the variable I will now have the character length of the string value.

14) Is it possible to initialize a variable at the time it was declared?

Yes, you don’t have to write a separate assignment statement after the variable declaration, unless you plan to change it later on.  For example:char planet[15] = “Earth”;does two things: it declares a string variable named planet, then initializes it with the value “Earth”.