C Programming Interview Questions
Q1. What is the use of main( ) in C?
main() function is the function from where execution of any C program begins. So, main() function is mandatory for any C program.
Q2. What is the difference b/w include preprocessor using < and " ?
#include<filename> and #include"filename"?
The difference is in the location where the preprocessor searches for the included file.
For #include "filename" the preprocessor searches in the same directory as the file containing the directive. This method is normally used to include programmer-defined header files.
For #include < filename > the preprocessor searches in an implementation dependent manner, normally in search directories pre-designated by the compiler/IDE. This method is normally used to include standard library header files.
Q3. What is the use of return value (int) of main function in C?
C's main function returns an int... that int goes to the program which executed it (the parent process, if you will) as an exit status code.
Specifically, on most operating systems, a 0 exit code signifies a normal run (no real errors), and non-zero means there was a problem and the program had to exit abnormally.
Q4. What are header files and what are its uses in C programming?
Header files are also known as library files.
They contain the prototypes of functions being used in a program.
The file extension is .h
Q5. What does the format %10.2 mean when included in a printf statement?
This format is used for two things: to set the number of spaces allotted for the output number and to set the number of decimal places.
The number before the decimal point is for the allotted space, in this case it would allot 10 spaces for the output number.
If the number of space occupied by the output number is less than 10, addition space characters will be inserted before the actual output number.
The number after the decimal point sets the number of decimal places, in this case, it?s 2 decimal spaces.
Q6. What are reserved words/Keywords?
Reserved words are words that are part of the standard C language library.
This means that reserved words have special meaning and therefore cannot be used for purposes other than what it is originally intended for.
Q7. What is data type in programming?
Data types in C language are defined as the data storage format that a variable can store a data to perform a specific operation.
Data types are used to define a variable before to use in a program.
Size of variable, constant and array are determined by data types.
Q8. What is compiler?
Compiler is a program that converts human readable code into machine readable code. This process is called compilation.
Q9. Difference between assembler, compiler and interpreter?
Assembler is a program that converts assembly level language (low level language) into machine level language.
Compiler compiles entire C source code into machine code.
Whereas, interpreters converts source code into intermediate code and then this intermediate code is executed line by line.
Q10. What is variable initialization and why is it important?
This refers to the process wherein a variable is assigned an initial value before it is used in the program.
Without initialization, a variable would have an unknown value, which can lead to unpredictable outputs when used in computations or other operations.
Q11. Difference between Source Codes and Object Codes?
Source codes are codes that were written by the programmer. It is made up of the commands and other English-like keywords that are supposed to instruct the computer what to do.
However, computers would not be able to understand source codes. Therefore, source codes are compiled using a compiler. The resulting outputs are object codes, which are in a format that can be understood by the computer processor.
In C programming, source codes are saved with the file extension .C, while object codes are saved with the file extension .OBJ
Q12. What is a newline escape sequence?
A newline escape sequence is represented by the \n character.
This is used to insert a new line when displaying data in the output screen.
More spaces can be added by inserting more \n characters.
Q13. What is global variable in C?
The variables which are having scope/life throughout the program are called global variables.
Global variable is defined outside the main function. So, this variable is visible to main function and all other sub functions.
Q14. What is local variable in C?
The variables which are having scope/life only within the function are called local variables.
These variables are declared within the function and can't be accessed outside the function.
Q15. What is sizeof( ) function in C ?
sizeof() function is used to find the memory space allocated for each data type in C.
Q16. Difference b/w auto and register variables ?
Storage class of all variables are auto by default unless we specify a variable is register or static or extern in C program.
Both auto variable and register variable are local variables.
Register variables are stored in register memory.
Whereas, auto variables are stored in main CPU memory.
Q17. Difference b/w auto and static variables ?
Both auto and static variables are local variables.
Static variables can retain the value of the variable between different function calls.
Q18. Difference b/w pre and post increment(++) operator ?
Pre increment operator is used to increment variable value by 1 before assigning the value to the variable.
Post increment operator is used to increment variable value by 1 after assigning the value to the variable.
Q19. Difference b/w exit and return statements ?
exit(0); is a system call which terminates current process/program.
Whereas, return 0; is a C language instruction/statement and it returns from the current function.
Q20. What is #define in C ?
#define is a pre-processor directive which is used to represent constant value.
This constant can be any of the basic data types and will replace by the value in the program at compile time..