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C Programming - Input / Output

Exercise : Input / Output - Point Out Errors
1.
Point out the error in the program? 
#include<stdio.h>
#include<stdlib.h>

int main()
{
    unsigned char;
    FILE *fp;
    fp=fopen("trial", "r");
    if(!fp)
    {
        printf("Unable to open file");
        exit(1);
    }
    fclose(fp);
    return 0;
}
Error: in unsigned char statement
Error: unknown file pointer
No error
None of above
Answer: Option
Explanation:

This program tries to open the file trial.txt in read mode. If file not exists or unable to read it prints "Unable to open file" and then terminate the program.

If file exists, it simply close the file and then terminates the program.

2.
Point out the error in the program? 
#include<stdio.h>

int main()
{
    char ch;
    int i;
    scanf("%c", &i);
    scanf("%d", &ch);
    printf("%c %d", ch, i);
    return 0;
}
Error: suspicious char to in conversion in scanf()
Error: we may not get input for second scanf() statement
No error
None of above
Answer: Option
Explanation:
No answer description is available. Let's discuss.
3.
Point out the error in the program? 
#include<stdio.h>

int main()
{
    FILE *fp;
    fp=fopen("trial", "r");
    fseek(fp, "20", SEEK_SET);
    fclose(fp);
    return 0;
}
Error: unrecognised Keyword SEEK_SET
Error: fseek() long offset value
No error
None of above
Answer: Option
Explanation:
Instead of "20" use 20L since fseek() need a long offset value.
4.
Point out the error in the program? 
#include<stdio.h>

/* Assume there is a file called 'file.c' in c:\tc directory. */
int main()
{
    FILE *fp;
    fp=fopen("c:\tc\file.c", "r");    
    if(!fp) 
      printf("Unable to open file.");        

    fclose(fp);
    return 0;
}
No error, No output.
Program crashes at run time.
Output: Unable to open file.
None of above
Answer: Option
Explanation:
The path of file name must be given as "c:\\tc\file.c"
5.
Point out the error/warning in the program? 
#include<stdio.h>

int main()
{
    unsigned char ch;
    FILE *fp;
    fp=fopen("trial", "r");
    while((ch = getc(fp))!=EOF)
        printf("%c", ch);
    fclose(fp);
    return 0;
}
Error: in unsigned char declaration
Error: while statement
No error
It prints all characters in file "trial"
Answer: Option
Explanation:
Here, EOF is -1. As 'ch' is declared as unsigned char it cannot deal with any negative value.
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