October 31, 2018

Sreekanth B

Gartner Most Frequently Asked C Language Interview Questions Answers

What is the significance of an algorithm to C programming?

Before a program can be written, an algorithm has to be created first. An algorithm provides a step by step procedure on how a solution can be derived. It also acts as a blueprint on how a program will start and end, including what process and computations are involved.

What is the advantage of an array over individual variables?

When storing multiple related data, it is a good idea to use arrays. This is because arrays are named using only 1 word followed by an element number. For example: to store the 10 test results of 1 student, one can use 10 different variable names (grade1, grade2, grade3… grade10). With arrays, only 1 name is used, the rest are accessible through the index name (grade[0], grade[1], grade[2]… grade[9]).

Write a loop statement that will show the following output:

1
12
123
1234
12345

Answer:

for (a=1; a<=5; i++) {
for (b=1; b<=a; b++)
printf("%d",b);
printf("\n");
}

What is wrong in this statement?  scanf(“%d”,whatnumber);

An ampersand & symbol must be placed before the variable name whatnumber. Placing & means whatever integer value is entered by the user is stored at the “address” of the variable name. This is a common mistake for programmers, often leading to logical errors.
Gartner Most Frequently Asked C Language Interview Questions Answers
Gartner Most Frequently Asked C Language Interview Questions Answers

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.

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.

What are comments and how do you insert it in a C program?

Comments are a great way to put some remarks or description in a program. It can serves as a reminder on what the program is all about, or a description on why a certain code or function was placed there in the first place. Comments begin with /* and ended by */ characters. Comments can be a single line, or can even span several lines. It can be placed anywhere in the program.

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.

What are binary trees?

Binary trees are actually an extension of the concept of linked lists. A binary tree has two pointers, a left one and a right one. Each side can further branch to form additional nodes, which each node having two pointers as well.

Not all reserved words are written in lowercase. TRUE or FALSE?

FALSE. All reserved words must be written in lowercase; otherwise the C compiler would interpret this as unidentified and invalid.

What is the difference between the expression “++a”  and “a++”?

In the first expression, the increment would happen first on variable a, and the resulting value will be the one to be used. This is also known as a prefix increment. In the second expression, the current value of variable a would the one to be used in an operation, before the value of a itself is incremented. This is also known as postfix increment.

What would happen to X in this expression: X += 15;  (assuming the value of X is 5)

X +=15 is a short method of writing X = X + 15, so if the initial value of X is 5, then 5 + 15 = 20.

In C language, the variables NAME, name, and Name are all the same. TRUE or FALSE?

FALSE. C language is a case sensitive language. Therefore, NAME, name and Name are three uniquely different variables.

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