Exercise: Input Output

Questions for: Input Output

What will be the output of the program ? 
#include<stdio.h>

int main()
{
    float a=3.15529;
    printf("%2.1f\n", a);
    return 0;
}
A:
3.00
B:
3.15
C:
3.2
D:
3
Answer: C

float a=3.15529; The variable a is declared as an float data type and initialized to value 3.15529;

printf("%2.1f\n", a); The precision specifier tells .1f tells the printf function to place only one number after the .(dot).

Hence the output is 3.2

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If the file 'source.txt' contains a line "Be my friend" which of the following will be the output of below program? 
#include<stdio.h>

int main()
{
    FILE *fs, *ft;
    char c[10];
    fs = fopen("source.txt", "r");
    c[0] = getc(fs);
    fseek(fs, 0, SEEK_END);
    fseek(fs, -3L, SEEK_CUR);
    fgets(c, 5, fs);
    puts(c);
    return 0;
}
A:
friend
B:
frien
C:
end
D:
Error in fseek();
Answer: C

The file source.txt contains "Be my friend".

fseek(fs, 0, SEEK_END); moves the file pointer to the end of the file.

fseek(fs, -3L, SEEK_CUR); moves the file pointer backward by 3 characters.

fgets(c, 5, fs); read the file from the current position of the file pointer.

Hence, it contains the last 3 characters of "Be my friend".

Therefore, it prints "end".

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What will be the output of the program ? 
#include<stdio.h>
char *str = "char *str = %c%s%c; main(){ printf(str, 34, str, 34);}";

int main()
{
    printf(str, 34, str, 34);
    return 0;
}
A:
char *str = "char *str = %c%s%c; main(){ printf(str, 34, str, 34);}"; main(){ printf(str, 34, str, 34);}
B:
char *str = %c%s%c; main(){ printf(str, 34, str, 34);}
C:
No output
D:
Error in program
Answer: A
No answer description is available. Let's discuss.
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What will be the output of the program ? 
#include<stdio.h>

int main()
{
    int k=1;
    printf("%d == 1 is" "%s\n", k, k==1?"TRUE":"FALSE");
    return 0;
}
A:
k == 1 is TRUE
B:
1 == 1 is TRUE
C:
1 == 1 is FALSE
D:
K == 1 is FALSE
Answer: B

Step 1: int k=1; The variable k is declared as an integer type and initialized to '1'.

Step 2: printf("%d == 1 is" "%s\n", k, k==1?"TRUE":"FALSE"); becomes

=> k==1?"TRUE":"FALSE"

=> 1==1?"TRUE":"FALSE"

=> "TRUE"

Therefore the output of the program is 1 == 1 is TRUE

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What will be the content of 'file.c' after executing the following program? 
#include<stdio.h>

int main()
{
    FILE *fp1, *fp2;
    fp1=fopen("file.c", "w");
    fp2=fopen("file.c", "w");
    fputc('A', fp1);
    fputc('B', fp2);
    fclose(fp1);
    fclose(fp2);
    return 0;
}
A:
B
B:
A
B
C:
B
B
D:
Error in opening file 'file1.c'
Answer: A

Here fputc('A', fp1); stores 'A' in the file1.c then fputc('B', fp2); overwrites the contents of the file1.c with value 'B'. Because the fp1 and fp2 opens the file1.c in write mode.

Hence the file1.c contents is 'B'.

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