C Aptitude Questions and answers with explanation

C Aptitude 28
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.

Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

–>
Predict the output or error(s) for the following:

C aptitude 28.1

 main()
{
char *p="hai friends",*p1;
p1=p;
while(*p!='') ++*p++;
printf("%s %s",p,p1);
}

Answer: ibj!gsjfoet

Explanation: ++*p++ will be parse in the given order
 *p that is value at the location currently pointed by p will be taken
  ++*p the retrieved value will be incremented
 when ; is encountered the location will be incremented that is p++ will be executed

Hence, in the while loop initial value pointed by p is ‘h’, which is changed to ‘i’ by executing ++*p and pointer moves to point, ‘a’ which is similarly changed to ‘b’ and so on. Similarly blank space is converted to ‘!’. Thus, we obtain value in p becomes “ibj!gsjfoet” and since p reaches ‘’ and p1 points to p thus p1doesnot print anything.

C aptitude 28.2

   #include <stdio.h>
#define a 10
main()
{
#define a 50
printf("%d",a);
}

Answer: 50

Explanation:The preprocessor directives can be redefined anywhere in the program. So the most recently assigned value will be taken.

C aptitude 28.3

     
main()
{
printf("%p",main);
}


Answer:Some address will be printed.
Explanation: Function names are just addresses (just like array names are addresses). main() is also a function. So the address of function main will be printed. %p in printf specifies that the argument is an address. They are printed as hexadecimal numbers.

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C Program to delete a file using remove function.

Write a C program to delete a specified file using remove function.
remove function deletes the specified file, where it takes file name as the argument and if file is successively deleted it returns 0 , other wise returns a non zero value.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

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* programs for commercial purposes,
* contact info@c-program-example.com
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* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<string.h>
int main()
{
    char file_name[40];
    printf("Enter the file name with location:n Example, c:example.txtnn");
    gets(file_name);
    if(remove(file_name) != 0 )
    puts("Error deleting filenn");
    else
    puts("File successfully deletednn");
    return 0;
}
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C program without using main function

Write a C program without using main function.
In this program, we didn’t use the main function, but we are using the preprocessor directive #define with arguments to define the Main function.
A Preprocessor is program which processes the source code before compilation.
The ‘##‘ operator is called the token pasting or token merging operator. In the second line of program we used it to merges the 4th,1st,3rd & the 2nd characters(tokens), and it compiles as “msut”.
When the controller calls int begin, preprocessor replaces the macro “begin” with the expansion decode(a,n,i,m,a,t,e). As defined in the macro decode it merges the 4th,1st,3rd & the 2nd characters, and int begin becomes int main(), so program runs successfully. Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.
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* programs for commercial purposes,
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* and browse!
*
* Happy Coding
***********************************************************/

#include<stdio.h>
#define decode(s,t,u,m,p,e,d) m##s##u##t
#define begin decode(a,n,i,m,a,t,e)

int begin()

{
printf(” Ha HA see how it is?? “);
}
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C program to print given numbers as a pyramid

Write a C program to print given numbers as a pyramid.
In this program we use the simple for statements to produce the patterns.
This program prints the following output,
        1
      232
    34543
  4567654
567898765
 Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

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* and browse!
*
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***********************************************************/

#include<stdio.h>


void display(int start, char *str){

int i,j;


for(i=start; i<=(start+start); i++)

printf("%c",str[i]);

for(j=i-2;j>=start;j--)

printf("%c",str[j]);

}


main(){

char str[]="123456789";

int i, j;

for(i=0;i<5;i++){

display(i, str);

printf("n");

}

}
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C Aptitude Questions and answers with explanation

C Aptitude 24
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about how to prepare and write the C Aptitude Exams?
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

 

Predict the output or error(s) for the following:

C aptitude 24.1

main()

{

char str[4]="test";

printf("%s",str);


}

Answer: test#$634278621@!

Explanation: The character array has the memory just enough to hold the string “test” and doesn’t have enough space to store the terminating null character. So it prints the test correctly and continues to print garbage values till it accidentally comes across a NULL character.

C aptitude 24.2

 
main()

{

char * str = "hello";

char * ptr = str;

char least = 127;

while (*ptr++)

least = (*ptr <least ) ?*ptr :least;

printf("%d",least);

}

Answer: 0

Explanation: After ‘ptr’ reaches the end of the string the value pointed by ‘str’ is ‘’. So the value of ‘str’ is less than that of ‘least’. So the value of ‘least’ finally is 0.

C aptitude 24.3

     main()

{

int i = 257;

int *iPtr = &i;

printf("%d %d", *((char*)iPtr), *((char*)iPtr+1) );

}

Answer: 11

Explanation: The integer value 257 is stored in the memory as, 00000001 00000001, so the individual bytes are taken by casting it to char * and get printed.

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C Program to change the text colors.

Write a C Program to change the text colors.
In this program, we give the example of changing the text colors, background colors using conio.h library.
Syntax: void textcolor(int_color);
Here color is the integer variable, you can specify a color name also, but it should be a proper color name in capital letters.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

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* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
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* and browse!
*
* Happy Coding
***********************************************************/

#include<stdio.h>
#include<conio.h>
int main()
{
clrscr();
textcolor(BLUE); // Change font colour to blue
textbackground(WHITE); //change the background colour to white
cprintf("Color is Blue with white backgroundnn");
clrscr();
textcolor(RED+BLINK);//this one is blinking the text
cprintf("Color is RED with blinkingnn");
return 0;
}
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C Aptitude Questions and answers with explanation

C Aptitude 23
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about how to prepare and write the C Aptitude Exams?
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

 

Predict the output or error(s) for the following:

C aptitude 23.1

void main(){
int res;
res= 56>76 ? return 0:return 1;
printf("%d",res);
}

Answer: Compilation error.

Explanation: We cannot use return keyword in conditional operator.

C aptitude 23.2
Note: here input for command line argument is, example 5 4 7 8

 
/* example.c */
#include

int main(int argc, char *argv[])
{
int j;
j = argv[1] + argv[2] + argv[3] + argv[4];
printf("%d", j);
return 0;
}

Answer: Error

Explanation: Command line arguments are string types, we can’t add or do the arithmetic operations on string types in C, we have to convert the argv[] to the integer types using atoi function.

C aptitude 23.3

     int main()
{
int num1 = 123;
float num2 = 123.0;
if(num1 == num2)
printf("num1 and num2 are equal");
else
printf("num1 and num2 are not equal");
return 0;
}

Answer: num1 and num2 are equal

Explanation: This is the tricky question, in if statement we are comparing 123=123.0, condition satisfied, so the result is num1 and num2 are equal.

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C program to sort a string

C Strings:
Write a C program to sort a string.
In this program we sort the string using bubble sort technique.
Bubble Sort is the simplest and easiest sorting technique. In this technique, the two successive items A[i] and A[i+1] are exchanged whenever A[i]>=A[i+1]. The larger values sink to the bottom of the array and hence it is called sinking sort. The end of each pass smaller values gradually “bubble” their way upward to the top(like air bubbles moving to surface of water) and hence called bubble sort.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

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* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
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* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>
#include<string.h>
int main(){
    int i,j,n;
    char str[50],temp[50];
    printf("Enter a String:nn");
    scanf("%s",str);
    n=strlen(str);
    for(i=0;i<=n;i++)
    for(j=i+1;j<=n;j++){
        if(strcmp(str[i],str[j])>0){
            strcpy(temp,str[i]);
            strcpy(str[i],str[j]);
            strcpy(str[j],temp);
        }
    }
    printf("The sorted string is:%sn",str);
    return 0;
}
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C Aptitude Questions and answers with explanation

C Aptitude 21
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 21.1

 char *Fun1()
{
char temp[ ] = “example";
return temp;
}
char *Fun2()
{
char temp[ ] = {‘e’, ‘x’,’a’,’m’,’p’,’l’,'e'};
return temp;
}
int main()
{
puts(Fun1());
puts(Fun2());
}


Answer: Garbage values.

Explanation: Both the functions suffer from the problem of dangling pointers. In Fun1() temp is a character array and so the space for it is allocated in heap and is initialized with character string “string”. This is created dynamically as the function is called, so is also deleted dynamically on exiting the function so the string data is not available in the calling function main() leading to print some garbage values. The function Fun2() also suffers from the same problem but the problem can be easily identified in this case.

C aptitude 21.2

   char *strexp()
{
char *temp = "example string";
return temp;
}
int main()
{
puts(strexp);
}

Answer: example string

Explanation: The character constants are stored in code/data area and not allocated in stack, so this doesn’t lead to dangling pointers.

C aptitude 21.3

     main()
{
int i=0;
while(+(+i--)!=0)
i-=i++;
printf("%d",i);
}

Answer: -1

Explanation: Unary + is the only dummy operator in C. So it has no effect on the expression and now the while loop is, while(i–!=0) which is false and so breaks out of while loop. The value –1 is printed due to the post-decrement operator.

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C Aptitude Questions and answers with explanation

C Aptitude 20
C program is one of most popular programming language which is used for core level of coding across the board. C program is used for operating systems, embedded systems, system engineering, word processors,hard ware drivers, etc.

In this site, we have discussed various type of C programs till date and from now on, we will move further by looking at the C aptitude questions.

In the coming days, we will post C aptitude questions, answers and explanation for interview preparations.

The C aptitude questions and answers for those questions along with explanation for the interview related queries.

We hope that this questions and answers series on C program will help students and freshers who are looking for a job, and also programmers who are looking to update their aptitude on C program.
Some of the illustrated examples will be from the various companies, and IT industry experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.

Predict the output or error(s) for the following:

C aptitude 20.1

  main()
{
int *j;
{
int i=10;
j=&i;
}
printf("%d",*j);
}


Answer: 10

Explanation: The variable i is a block level variable and the visibility is inside that block only. But the lifetime of i is lifetime of the function so it lives up to the exit of main function. Since the i is still allocated space, *j prints the value stored in i since j points i.

C aptitude 20.2

   main()
{
int i=-1;
-i;
printf("i = %d, -i = %d n",i,-i);
}


Answer: i = -1, -i = 1

Explanation: -i is executed and this execution doesn’t affect the value of i. In printf first you just print the value of i. After that the value of the expression -i = -(-1) is printed.

C aptitude 20.3

     main()
{
const int i=4;
float j;
j = ++i;
printf("%d %f", i,++j);
}

Answer: Compiler error

Explanation: i is a constant. you cannot change the value of constant

C aptitude 20.4

      main()
{
int a[2][2][2] = { {10,2,3,4}, {5,6,7,8} };
int *p,*q;
p=&a[2][2][2];
*q=***a;
printf("%d..%d",*p,*q);
}

Answer: garbagevalue..1

Explanation: p=&a[2][2][2] you declare only two 2D arrays. but you are trying to access the third 2D(which you are not declared) it will print garbage values. *q=***a starting address of a is assigned integer.

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