C Programming Library Functions Online Test, C Programming MCQ

rewind() takes the file pointer to the beginning of the file. so that the next I/O operation will take place at the beginning of the file.
Example: rewind(FilePointer);

strrchr() returns a pointer to the last occurrence of character in a string.

Example:

#include <stdio.h>
#include <string.h>

int main()
{
    char str[30] = "12345678910111213";
    printf("The last position of '2' is %d.\n",
            strrchr(str, '2') - str);
    return 0;
}

1. itoa() converts an integer to a string.
2. ltoa() converts a long to a string.
3. ultoa() converts an unsigned long to a string.
4. sprintf() sends formatted output to a string, so it can be used to convert any type of values to string type.

#include<stdio.h>
#include<stdlib.h>

int main(void)
{
   int   num1 = 12345;
   float num2 = 5.12;
   char str1[20];
   char str2[20];

   itoa(num1, str1, 10); /* 10 radix value */
   printf("integer = %d string = %s \n", num1, str1);

   sprintf(str2, "%f", num2);
   printf("float = %f string = %s", num2, str2);

   return 0;
}

// Output:
// integer = 12345 string = 12345
// float = 5.120000 string = 5.120000

“fflush()” flush any buffered output associated with filename, which is either a file opened for writing or a shell command for redirecting output to a pipe or coprocess.

Example:
fflush(FilePointer);
fflush(NULL); flushes all streams.

The randomize() function initializes the random number generator with a random value based on time. You can try the sample program given below in Turbo-C, it may not work as expected in other compilers.

/* Prints a random number in the range 0 to 99 */

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

int main(void)
{
    randomize();
    printf("Random number in the 0-99 range: %d\n", random (100));
    return 0;
}

In the program, printf() returns the number of charecters printed on the console

i = printf(“How r u\n”); This line prints “How r u” with a new line character and returns the length of string printed then assign it to variable i.
So i = 8 (length of ‘\n’ is 1).

i = printf(“%d\n”, i); In the previous step the value of i is 8. So it prints “8” with a new line character and returns the length of string printed then assign it to variable i. So i = 2 (length of ‘\n’ is 1).

printf(“%d\n”, i); In the previous step the value of i is 2. So it prints “2”.

Both ceil() and floor() return the integer found as a double.

floor(2.5) returns the largest integral value(round down) that is not greater than 2.5. So output is 2.000000.

ceil(2.5) returns 3, while converting the double to int it returns ‘0’.
So, the output is ‘2.000000, 0’.

scanf() returns the number of variables to which you are provding the input.

i = scanf(“%d %d”, &i, &i); Here Scanf() returns 2. So i = 2.

printf(“%d\n”, i); Here it prints 2.

The ungetc() function pushes the character c back onto the named input stream, which must be open for reading.

This character will be returned on the next call to getc or fread for that stream.

One character can be pushed back in all situations.

A second call to ungetc without a call to getc will force the previous character to be forgotten.

Function atoi() converts the string to integer.
Function atof() converts the string to float.

result1 = result1+atoi(i);
Here result1 = 10 + atoi(55.555);
result1 = 10 + 55;
result1 = 65;

result2 = result2+atof(i);
Here result2 = 11.111 + atof(55.555);
result2 = 11.111 + 55.555000;
result2 = 66.666000;
So the output is “65, 66.666000” .

memcmp compares the first 2 bytes of the blocks dest and src as unsigned chars. So, the ASCII value of 97 is ‘a’.

if((i = memcmp(dest, src, 2))==0) When comparing the array dest and src as unsigned chars, the first 2 bytes are same in both variables.so memcmp returns ‘0’.
Then, the if(0=0) condition is satisfied. Hence the output is “Got it”.

The gcvt() function converts a floating-point number to a string. It converts given value to a null-terminated string.

#include <stdlib.h>
#include <stdio.h>

int main(void)
{
    char str[25];
    double num;
    int sig = 5; /* significant digits */

    /* a regular number */
    num = 9.876;
    gcvt(num, sig, str);
    printf("string = %s\n", str);

    /* a negative number */
    num = -123.4567;
    gcvt(num, sig, str);
    printf("string = %s\n", str);

    /* scientific notation */
    num = 0.678e5;
    gcvt(num, sig, str);
    printf("string = %s\n", str);

    return(0);
}

Output:
string = 9.876
string = -123.46
string = 67800

for(i=1; i<=5; i++) Here the for loop runs 5 times.

Loop 1:
scanf(“%c”, &c); Here we give ‘a’ as input.
printf(“%c”, c); prints the character ‘a’ which is given in the previous “scanf()” statement.
ungetc(c, stdin); “ungetc()” function pushes character ‘a’ back into input stream.

Loop 2:
Here the scanf(“%c”, &c); get the input from “stdin” because of “ungetc” function.
printf(“%c”, c); Now variable c = ‘a’. So it prints the character ‘a’.
ungetc(c, stdin); “ungetc()” function pushes character ‘a’ back into input stream.

This above process will be repeated in Loop 3, Loop 4, Loop 5.

Declaration Syntax:
int fprintf (FILE *stream, const char *format [, argument, …]);

Example:
fprintf(filestream, “%s %d %s”, Name, Age, City);

Declaration:
void *memccpy(void *dest, const void *src, int c, size_t n); : Copies a block of n bytes from src to dest

With memccpy(), the copying stops as soon as either of the following occurs:
=> the character ‘i’ is first copied into str2
=> n bytes have been copied into str2

C string is a character sequence stored as a one-dimensional character array and terminated with a null character(‘\0’, called NULL in ASCII).
The length of a C string is found by searching for the (first) NULL byte.

FILE – a structure containing the information about a file or text stream needed to perform input or output operations on it, including:
=> a file descriptor, the current stream position,
=> an end-of-file indicator,
=> an error indicator,
=> a pointer to the stream’s buffer, if applicable

fpos_t – a non-array type capable of uniquely identifying the position of every byte in a file.
size_t – an unsigned integer type which is the type of the result of the sizeof operator.

The ftell() function shall obtain the current value of the file-position indicator for the stream pointed to by stream.

Example:

#include <stdio.h>

int main(void)
{
    FILE *stream;
    stream = fopen("MYFILE.TXT", "w+");
    fprintf(stream, "This is a test");
    printf("The file pointer is at byte %ld\n", ftell(stream));
    fclose(stream);
    return 0;
}

fwrite() – Unformatted write in to a file.
fscanf() – Formatted read from a file.

g = strcmp(s1, s2); returns 0 when the strings are equal, a negative integer when s1 is less than s2, or a positive integer if s1 is greater than s2, that strcmp() not only returns -1, 0 and +1, but also other negative or positive values(returns difference between the first non-matching pair of characters between s1 and s2).

A possible implementation for strcmp() in “The Standard C Library”.

int strcmp (const char * s1, const char * s2)
{                
    for(; *s1 == *s2; ++s1, ++s2) 
    {
        if(*s1 == 0)
            return 0;
    }
    return *(unsigned char *)s1 < *(unsigned char *)s2 ? -1 : 1;
}

The C standard library consists of a set of sections of the ISO C standard which describe a collection of header files and library routines used to implement common operations, such as input/output and string handling, in the C programming language. The C standard library is an interface standard described by a document; it is not an actual library of software routines available for linkage to C programs.

No. It will print something like ‘IndiaBIX(some garbage values here)’ .

Because after copying the first 8 characters of source string into target string strncpy() doesn’t terminate the target string with a ‘\0’. So it may print some garbage values along with IndiaBIX.

itoa() takes the integer input value input and converts it to a number in base radix. The resulting number a sequence of base-radix digits.

Example:

/* itoa() example */
#include <stdio.h>
#include <stdlib.h>

int main ()
{
    int no;
    char buff [50];
    printf ("Enter number: ");
    scanf ("%d",&no);
    
    itoa (no,buff,10);
    printf ("Decimal: %s\n",buff);
    
    itoa (no,buff,2);
    printf ("Binary: %s\n",buff);
    
    itoa (no,buff,16);
    printf ("Hexadecimal: %s\n",buff);
    
    return 0;
}

Output:
Enter a number: 1250
Decimal: 1250
Binary: 10011100010
Hexadecimal: 4e2

scanf is a function that reads data with specified format from a given string stream source.
scanf(“%d”,&number);

atoi() convert string to integer.
var number;
number = atoi(“string”);