C Interview Questions and Answers

When is the void keyword used in a function?

When declare functions with void then it will not require return a value.

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What is C language?

C is a high-level programming language and first developed in 1972 by Dennis Ritchie and Ken Thompson at AT& T Bell Labs.

Why C is sometimes called a mid-level programming language?

C supports both low-level (machine) and high level programing that is why it is also known as a mid-level programming language.

What are the advantages and disadvantages of C language?

Advantage and disadvantage of C are
It is a high-level programming languages that is closer to human languages, especially English.
C programs can be reused, by saving into a library file and invoking simply by including the library file.
C allows to access computer hardware and peripherals. 
It used compiler, so once program become executable code then we can run it without interacting the compiler.

It used complier so complied code not portable on different machine.
C is a procedural language, become difficult to maintain for large application.
Less support to GUI.

What is a variable?

A variable is a name representation of memory storage location and that value can change between program execution.

What is the difference between variable declaration and variable definition?

Declaration associates type to the variable whereas definition is value assignment of the variable.

What is a constant?

When variables are declared with the const keywordcalled constant. The value ofconstant never changed.

What is the difference between local variable and global variable in C?

Local variable: A variable which is declared inside function or block is known as local variable.
Global variable: A variable which is declared outside function or block is known as global variable.

What is Storage Class in C and types of it?

The storage class represent scope and storage type in memory of variable in C.
There are four types of storage cases: Auto,Extern,Static and Register

What is auto keyword in C?

The auto keyword indicate that the memory location of a variable is temporary. Whereas by default every local variable of the function and block is automatic (auto). 

What is the use of static variable in C?

A variable declared with static keyword, is known as static variable. The static variable retains its value between multiple function calls and has permanent scope.

What are register variables? What are the advantages of using register variables? 

A variable is declared with a register storage class, known as register variable. The register variable is stored in the CPU register instead of main memory. 

Storing of frequently used variable in register might be speed up the code as variable access is faster from register in compare from memory. 

What is the purpose of type declarations? Or use of typedef?

The type declaration allow to create a name synonym for the existing data types that can help to simplify the complex declaration.

typedef type identifier; 

How do you know the size of a data type or variable?

The sizeof operator can measure the data type size.

What is type casting?

Converting one data type into another is known as type casting.

What is a function and advantages of it? 

A function is a block of set of instruction that perform specific task.
Reusability: function can be reuse in different place to perform same task
Code reduction: repeated code can move into function and can call function in place 
Modularity: task can be simplify by dividing that in modularity, that also increase readability

What is Recursive Functions?

The function can be called by another function and can call itself from a statement inside the body of the function itself. When function called itself then is said to be recursive.

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Pipes and Cistern

Two pipes A and B can fill a tank in 6 hours and 4 hours respectively. If they are opened on alternate hours and if pipe A s opened first, in how many hours, the tank shall be full?

A large tanker can be filled by two pipes A and B in 60 min and 40 min respectively. How many minutes will it take to fill the tanker from empty state if B is used for first half of the time, and A and B fill it together for the other half?

A tank is filled by 3 pipes with uniform flow. The first two pipes operating simultaneously fill the tank in the same time during which the tank is filled by the third pipe alone. The 2nd pipe fills the tank 5 hours faster than first pipe and 4 hours slower than third pipe. The time required by first pipe is?

Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill the cistern. How much time will be taken by A to fill the cistern separately?

Two pipes A and B can fill a tank in 24 min and 32 min respectively. If both the pipes are opened simultaneously, after how much time B should be closed so that the tank is full in 18 min?

Two pipes A and B can fill a tank in 36 min and 45 min respectively. A water pipe C can empty the tank in 30 min. First A and B are opened. after 7 min, C is also opened. In how much time, the tank is full?

Two pipes can fill a cistern in 14 hours and 16 hours respectively. The pipes are opened simultaneously and it is found that due to leakage in the bottom it took 32 min more to fill the cistern. When the cistern is full, in what time will the leak empty it?

Bucket P has thrice the capacity as Bucket Q. It takes 60 turns for Bucket P to fill the empty drum. How many turns it will take for both the buckets P and Q, having each turn together to fill the empty drum?


In a class , 30 % of the students offered English, 20 % offered Hindi and 10 % offered Both.If a student is offered at random, what is the probability that he has offered English or Hindi?

In a lottery ,there are 10 prizes and 25 blanks.A lottery is drawn at random. what is the probability of getting a prize ?

Two dice are thrown simultaneously .what is the probability of getting two numbers whose product is even?

Two diced are tossed the probability that the total score is a prime number?

Two cards are drawn at random from a pack of 52 cards What is the probability that either both are black or both are queens?

Two dice are thrown together .What is the probability that the sum of the number on the two faces is divisible by 4 or 6?

A bag contains 6 white and 4 black balls .Two balls are drawn at random .Find the probability that they are of the same colour?

In a simultaneous throw of a pair of dice,find the probability of getting a total more than 7?

An unbiased die is tossed.Find the probability of getting a multiple of 3?

Problems on Ages

My brother is 3 years elder to me. My father was 28 years of age when my sister was born while my mother was 26 years of age when i was born. If my sister was 4 years of age when my brother was born,then what was the age my father and mother respectively when my brother was born?

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