C Interview Questions and Answers

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
Advantages
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.

Disadvantages 
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.

Syntax
typedef type identifier; 

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General Knowledge of World

Which country will host the 2022 Football World Cup?

Area

The angles of a triangle are in the ratio 2 : 4 : 3. The smallest angle of the triangle is?

Which one of the following triples does not represent the sides of a triangle?

If the perimeter of a rectangle is 10 cm and the area is 4 cm2, then its length is?

Height and Distance

An aeroplane flying at a height of 300 m above the ground passes vertically above another plane at an instant when the angles of elevation of the two planes from the same point on the ground are 60º and 45º respectively. What is the height of the lower plane from the ground?

From the top of a building 90 m high, the angles of depression of the top and the bottom of a tree are 30º and 45º respectively. What is the height of the tree?

Trigonometry

What is the value of sinx √( 1 /1+cosx + 1 /1-cosx ) ?

What is cos4 A - sin4 A / cos2 A - sin2 A equal to?

If 7sin2 x +3cos2 x = 4, 0 < x < 90º ,then what is the value of tan x?

If x = a cosθ + b sinθ and y = a sinθ - b cosθ then what is x2 + y2 equal to?

Average

The mean of 5 numbers is 15. If one more number is included, the mean of the 6 numbers becomes 17. What is the included number?

The mean marks obtained by 300 students in a subject are 60. The mean of top 100 students was found to be 80 and the mean of last 100 students was found to be 50. The mean marks of the remaining 100 students are?

In an asymmetrical distribution, of the mean and median of the distribution are 270 and 220 respectively, then the mode of the data is?

Let a, b, c, d, e, f, g be consecutive even numbers and j, k, l, m, n be consecutive odd numbers. What is the average of all the numbers?

Alligation or Mixture

25 kg of alloy X is mixed with 125 kg of alloy Y. If the amount of lead and tin in the alloy X is the ratio 1 : 2 and the amount of lead and tin in the alloy Y is in the ratio 2 : 3, then what is the ratio of lead to tin in the mixture?

Simplification

The ratio of two numbers is 1 : 5 and their product is 320. What is the difference between the square of these two numbers?