What are compound statements?
Compound statements are made up of two or more program statements that are executed together. This usually occurs while handling conditions wherein a series of statements are executed when a TRUE or FALSE is evaluated. Compound statements can also be executed within a loop. Curly brackets { } are placed before and after compound statements.
Write a program to check Armstrong number in C?
#include<stdio.h>
#include<conio.h>
main()
{
int n,r,sum=0,temp; //declaration of variables.
clrscr(); //It clears the screen.
printf("enter the number=");
scanf("%d",&n);
temp=n;
while(n>0)
{
r=n%10;
sum=sum+(r*r*r);
n=n/10;
}
if(temp==sum)
printf("armstrong number ");
else
printf("not armstrong number");
getch(); //It reads a character from the keyword.
}
Write a program to reverse a given number in C?
#include<stdio.h>
#include<conio.h>
main()
{
int n, reverse=0, rem; //declaration of variables.
clrscr(); // It clears the screen.
printf("Enter a number: ");
scanf("%d", &n);
while(n!=0)
{
rem=n%10;
reverse=reverse*10+rem;
n/=10;
}
printf("Reversed Number: %d",reverse);
getch(); // It reads a character from the keyword.
}
What does the && 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.
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");
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.
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.
What is the use of a semicolon (;) at the end of every program statement?
It has to do with the parsing process and compilation of the code. A semicolon acts as a delimiter, so that the compiler knows where each statement ends, and can proceed to divide the statement into smaller elements for syntax checking.
What is difference between i++ and ++i?
1) The expression ‘i++’ returns the old value and then increments i. The expression ++i increments the value and returns new value.
2) Precedence of postfix ++ is higher than that of prefix ++.
3) Associativity of postfix ++ is left to right and associativity of prefix ++ is right to left.
4) In C++, ++i can be used as l-value, but i++ cannot be. In C, they both cannot be used as l-value.
What is l-value?
l-value or location value refers to an expression that can be used on left side of assignment operator. For example in expression “a = 3”, a is l-value and 3 is r-value.
l-values are of two types:
“nonmodifiable l-value” represent a l-value that can not be modified. const variables are “nonmodifiable l-value”.
“modifiable l-value” represent a l-value that can be modified.
How to write your own sizeof operator?
#define my_sizeof(type) (char *)(&type+1)-(char*)(&type)
How will you print numbers from 1 to 100 without using loop?
We can use recursion for this purpose.
/* Prints numbers from 1 to n */
void printNos(unsigned int n)
{
if(n > 0)
{
printNos(n-1);
printf("%d ", n);
}
}
What is volatile keyword?
The volatile keyword is intended to prevent the compiler from applying any optimizations on objects that can change in ways that cannot be determined by the compiler.
Objects declared as volatile are omitted from optimization because their values can be changed by code outside the scope of current code at any time. See Understanding “volatile” qualifier in C for more details.
Can a variable be both const and volatile?
yes, the const means that the variable cannot be assigned a new value. The value can be changed by other code or pointer. For example the following program works fine.
int main(void)
{
const volatile int local = 10;
int *ptr = (int*) &local;
printf("Initial value of local : %d \n", local);
*ptr = 100;
printf("Modified value of local: %d \n", local);
return 0;
}
Write a program to print "hello world" without using a semicolon?
#include<stdio.h>
void main(){
if(printf("hello world")){} // It prints the ?hello world? on the screen.
}
Write a program to swap two numbers without using the third variable?
#include<stdio.h>
#include<conio.h>
main()
{
int a=10, b=20; //declaration of variables.
clrscr(); //It clears the screen.
printf("Before swap a=%d b=%d",a,b);
a=a+b;//a=30 (10+20)
b=a-b;//b=10 (30-20)
a=a-b;//a=20 (30-10)
printf("\nAfter swap a=%d b=%d",a,b);
getch();
}
Write a program to print Fibonacci series without using recursion?
#include<stdio.h>
#include<conio.h>
void main()
{
int n1=0,n2=1,n3,i,number;
clrscr();
printf("Enter the number of elements:");
scanf("%d",&number);
printf("\n%d %d",n1,n2);//printing 0 and 1
for(i=2;i<number;++i)//loop starts from 2 because 0 and 1 are already printed
{
n3=n1+n2;
printf(" %d",n3);
n1=n2;
n2=n3;
}
getch();
}
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.
What is || operator and how does it function in a program?
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.
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.
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.
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 then 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.
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 =.
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”);
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.
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”.
Why is C language being considered a middle level language?
This is because C language is rich in features that make it behave like a high level language while at the same time can interact with hardware using low level methods. The use of a well structured approach to programming, coupled with English-like words used in functions, makes it act as a high level language. On the other hand, C can directly access memory structures similar to assembly language routines.
What are the different file extensions involved when programming in C?
Source codes in C are saved with .C file extension. Header files or library files have the .H file extension. Every time a program source code is successfully compiled, it creates an .OBJ object file, and an executable .EXE file.
What are reserved words?
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. Examples of reserved words are int, void, and return.
What are linked list?
A linked list is composed of nodes that are connected with another. In C programming, linked lists are created using pointers. Using linked lists is one efficient way of utilizing memory for storage.
What is FIFO?
In C programming, there is a data structure known as queue. In this structure, data is stored and accessed using FIFO format, or First-In-First-Out. A queue represents a line wherein the first data that was stored will be the first one that is accessible as well.
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]).
Compound statements are made up of two or more program statements that are executed together. This usually occurs while handling conditions wherein a series of statements are executed when a TRUE or FALSE is evaluated. Compound statements can also be executed within a loop. Curly brackets { } are placed before and after compound statements.
Write a program to check Armstrong number in C?
#include<stdio.h>
#include<conio.h>
main()
{
int n,r,sum=0,temp; //declaration of variables.
clrscr(); //It clears the screen.
printf("enter the number=");
scanf("%d",&n);
temp=n;
while(n>0)
{
r=n%10;
sum=sum+(r*r*r);
n=n/10;
}
if(temp==sum)
printf("armstrong number ");
else
printf("not armstrong number");
getch(); //It reads a character from the keyword.
}
Write a program to reverse a given number in C?
#include<stdio.h>
#include<conio.h>
main()
{
int n, reverse=0, rem; //declaration of variables.
clrscr(); // It clears the screen.
printf("Enter a number: ");
scanf("%d", &n);
while(n!=0)
{
rem=n%10;
reverse=reverse*10+rem;
n/=10;
}
printf("Reversed Number: %d",reverse);
getch(); // It reads a character from the keyword.
}
What does the && 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.
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");
 |
| Daum Frequently Asked C Language Interview Questions Answers |
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.
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.
What is the use of a semicolon (;) at the end of every program statement?
It has to do with the parsing process and compilation of the code. A semicolon acts as a delimiter, so that the compiler knows where each statement ends, and can proceed to divide the statement into smaller elements for syntax checking.
What is difference between i++ and ++i?
1) The expression ‘i++’ returns the old value and then increments i. The expression ++i increments the value and returns new value.
2) Precedence of postfix ++ is higher than that of prefix ++.
3) Associativity of postfix ++ is left to right and associativity of prefix ++ is right to left.
4) In C++, ++i can be used as l-value, but i++ cannot be. In C, they both cannot be used as l-value.
What is l-value?
l-value or location value refers to an expression that can be used on left side of assignment operator. For example in expression “a = 3”, a is l-value and 3 is r-value.
l-values are of two types:
“nonmodifiable l-value” represent a l-value that can not be modified. const variables are “nonmodifiable l-value”.
“modifiable l-value” represent a l-value that can be modified.
How to write your own sizeof operator?
#define my_sizeof(type) (char *)(&type+1)-(char*)(&type)
How will you print numbers from 1 to 100 without using loop?
We can use recursion for this purpose.
/* Prints numbers from 1 to n */
void printNos(unsigned int n)
{
if(n > 0)
{
printNos(n-1);
printf("%d ", n);
}
}
What is volatile keyword?
The volatile keyword is intended to prevent the compiler from applying any optimizations on objects that can change in ways that cannot be determined by the compiler.
Objects declared as volatile are omitted from optimization because their values can be changed by code outside the scope of current code at any time. See Understanding “volatile” qualifier in C for more details.
Can a variable be both const and volatile?
yes, the const means that the variable cannot be assigned a new value. The value can be changed by other code or pointer. For example the following program works fine.
int main(void)
{
const volatile int local = 10;
int *ptr = (int*) &local;
printf("Initial value of local : %d \n", local);
*ptr = 100;
printf("Modified value of local: %d \n", local);
return 0;
}
Write a program to print "hello world" without using a semicolon?
#include<stdio.h>
void main(){
if(printf("hello world")){} // It prints the ?hello world? on the screen.
}
Write a program to swap two numbers without using the third variable?
#include<stdio.h>
#include<conio.h>
main()
{
int a=10, b=20; //declaration of variables.
clrscr(); //It clears the screen.
printf("Before swap a=%d b=%d",a,b);
a=a+b;//a=30 (10+20)
b=a-b;//b=10 (30-20)
a=a-b;//a=20 (30-10)
printf("\nAfter swap a=%d b=%d",a,b);
getch();
}
Write a program to print Fibonacci series without using recursion?
#include<stdio.h>
#include<conio.h>
void main()
{
int n1=0,n2=1,n3,i,number;
clrscr();
printf("Enter the number of elements:");
scanf("%d",&number);
printf("\n%d %d",n1,n2);//printing 0 and 1
for(i=2;i<number;++i)//loop starts from 2 because 0 and 1 are already printed
{
n3=n1+n2;
printf(" %d",n3);
n1=n2;
n2=n3;
}
getch();
}
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.
What is || operator and how does it function in a program?
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.
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.
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.
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 then 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.
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 =.
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”);
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.
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”.
Why is C language being considered a middle level language?
This is because C language is rich in features that make it behave like a high level language while at the same time can interact with hardware using low level methods. The use of a well structured approach to programming, coupled with English-like words used in functions, makes it act as a high level language. On the other hand, C can directly access memory structures similar to assembly language routines.
What are the different file extensions involved when programming in C?
Source codes in C are saved with .C file extension. Header files or library files have the .H file extension. Every time a program source code is successfully compiled, it creates an .OBJ object file, and an executable .EXE file.
What are reserved words?
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. Examples of reserved words are int, void, and return.
What are linked list?
A linked list is composed of nodes that are connected with another. In C programming, linked lists are created using pointers. Using linked lists is one efficient way of utilizing memory for storage.
What is FIFO?
In C programming, there is a data structure known as queue. In this structure, data is stored and accessed using FIFO format, or First-In-First-Out. A queue represents a line wherein the first data that was stored will be the first one that is accessible as well.
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]).