Question on console input output

Last Updated: Jan 19, 2013

Jan 19 • General, Notes, Opinion • 1853 Views • 1 Comment on Question on console input output

Q1: what is console input output?
ans:The I/O functions provide a simple way to read a stream of characters from console input or to write a stream of characters to console output. A read operation gets input characters from a console’s input buffer and stores them in a specified buffer. A high-level write operation takes characters from a specified buffer and writes them to a screen buffer at the current cursor location, advancing the cursor as each character is written.

Q2:explain briefly the concept of console input output?
ans:Input/Output is the interface between the computer and the outside world. Simple input/output consists of switches, relay contacts, indicators, etc. Two other classes of I/O are console I/O and mass storage I/O. The latter would include tape or disk or any other method (usually using magnetic medium) of storing and retrieving large records or files. I’m limiting my discussion here to console I/O.

Q3:What is the purpose of “rb” in fopen() function used below in the code?
FILE *fp;
fp = fopen(‘source.txt”,”rb”);
ans:The file source.txt will be opened in the binary mode.

Q4:What does fp point to in the program ?

#include

int main()
{
FILE *fp;
fp=fopen(“trial”, “r”);
return 0;
}

ans:A structure which contains a char pointer which points to the first character of a file.

Q5:To print out a and b given below, which of the following printf() statement will you use?

#include

float a=3.14;
double b=3.14;
ans:To print a float value, %f is used as format specifier.

To print a double value, %lf is used as format specifier.

Therefore, the answer is printf(“%f %lf”, a, b);

Q6:To scan a and b given below, which of the following scanf() statement will you use?

#include

float a;
double b;

ans:To scan a float value, %f is used as format specifier.

To scan a double value, %lf is used as format specifier.

Therefore, the answer is scanf(“%f %lf”, &a, &b);

Q7:Out of fgets() and gets() which function is safe to use?
ans:because, In fgets() we can specify the size of the buffer into which the string supplied will be stored.

Q8:Consider the following program and what will be content of t?

#include

int main()
{
FILE *fp;
int t;
fp = fopen(“DUMMY.C”, “w”);
t = fileno(fp);
printf(“%d\n”, t);
return 0;

ans:fp=fopen(“DUMMY.C”, “w”); A file DUMMY.C is opened in write mode and returns the file pointer to fp

t = fileno(fp); returns the handle for the fp stream and it stored in the variable t

printf(“%d\n”, t); It prints the handle number

Q9:Which files will get closed through the fclose() in the following program?

#include

int main()
{
FILE *fs, *ft, *fp;
fp = fopen(“A.C”, “r”);
fs = fopen(“B.C”, “r”);
ft = fopen(“C.C”, “r”);
fclose(fp, fs, ft);
return 0;
}

ans: Error in fclose() due to Extra parameter in call to fclose().

Q10:what is the error in the program?

#include

int main()
{
FILE *fp;
fp=fopen(“trial”, “r”);
fseek(fp, “20”, SEEK_SET);
fclose(fp);
return 0;
}

ans:Error: fseek() long offset value because Instead of “20” use 20L since fseek() need a long offset value.

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