What are the high level I/O functions in C language?

I/O refers to the input - output functions in C language.

High level I/O

• These are easily understood by human beings
• The advantage is portability.

Low level I/O

• These are easily understood by computer.
• The advantage is that execution time is less.
• The disadvantage is that Non portability.

High level I/O Functions

The high level input - output (I/O) functions are explained below −

fprintf ( ) & fscanf ( ) functions

• fprintf ( )

The syntax is as follows −

fprintf (file pointer, " control string”, variable list)

For example,

FILE *fp;
fprintf (fp, "%d%c”, a,b);

• fscanf ( )

The syntax is as follows −

fscanf(file pointer, "control string”, & variable list);

For example,

FILE *fp;
fscanf (fp, "%d%c”, &a,&b);

putc( ) and getc( ) functions

• putc ( )

It is used for writing a character into a file.

The syntax is as follows −

putc (char ch, FILE *fp);

For example,

FILE *fp;
char ch;
putc(ch, fp);

• get c ( )

It is used to read a character from file.

The syntax is as follows −

char getc (FILE *fp);

For example,

FILE *fp;
char ch;
ch = getc(fp);

putw ( ) and getw ( ) functions

• putw( )

It is used for writing a number into file.

The syntax is as follows −

putw (int num, FILE *fp);

For example,

FILE *fp;
int num;
putw(num, fp);

• getw ( )

It is used for reading a number from a file.

The syntax is as follows −

int getw (FILE *fp);

For example,

FILE *fp;
int num;
num = getw(fp);

fput c ( ) and fgetc ( ) functions

• fputc( )

It is used for writing a character in to a file.

The syntax is as follows −

fputc (char ch, FILE *fp);

For example,

FILE *fp;
char ch;
fputc (ch.fp);

• fgetc( )

It is used for reading a character from a file.

The syntax is as follows −

fputc (char ch, FILE *fp);

For example,

FILE *fp;
char ch;
ch = fgetc(fp);

fgets ( ) and fputs ( ) functions

• fgets ( )

It is used for reading a string from a file.

The syntax is as follows

fgets (string variable, No. of characters, File pointer);

For example,

FILE *fp;
char str [30];
fgets (str,30,fp);

• fputs ( )

It is used for writing a string into a file.

The syntax is as follows −

fputs (string variable, file pointer);

For example,

FILE *fp;
char str[30];
fputs (str,fp);

fread ( ) and fwrite ( ) functions

• fread ( )

It is used for reading entire record at a time.

The syntax is as follows −

fread( & structure variable, size of (structure variable), no of records, file pointer);

For example,

struct emp{
   int eno;
   char ename [30];
   float sal;
} e;
FILE *fp;
fread (&e, sizeof (e), 1, fp);

• fwrite ( )

It is used for writing an entire record at a time.

The syntax is as follows −

fwrite( & structure variable , size of structure variable, no of records, file pointer);

For example,

struct emp{
   int eno:
   char ename [30];
   float sal;
} e;
FILE *fp;
fwrite (&e, sizeof(e), 1, fp);

Example Program

Following is the C program for storing numbers from 1 to 10 and to print the same −

//Program for storing no’s from 1 to 10 and print the same
#include<stdio.h>
int main( ){
   FILE *fp;
   int i;
   fp = fopen ("num.txt", "w");
   for (i =1; i<= 10; i++){
      putw (i, fp);
   }
   fclose (fp);
   fp =fopen ("num.txt", "r");
   printf ("file content is");
   for (i =1; i<= 10; i++){
      i= getw(fp);
      printf ("%d",i);
   }
   fclose (fp);
   return 0;
}

Output

When the above program is executed, it produces the following result −

file content is12345678910

Given below is another C program for storing the details of 5 students into a file and print the same by using fread ( ) and fwrite ( ) −

Example

#include<stdio.h>
struct student{
   int sno;
   char sname [30];
   float marks;
   char temp;
};
main ( ){
   struct student s[60];
   int i;
   FILE *fp;
   fp = fopen ("student1.txt", "w");
   for (i=0; i<2; i++){
      printf ("enter details of student %d\n", i+1);
      printf("student number:");
      scanf("%d",&s[i].sno);
      scanf("%c",&s[i].temp);
      printf("student name:");
      gets(s[i].sname);
      printf("student marks:");
      scanf("%f",&s[i].marks);
      fwrite(&s[i], sizeof(s[i]),1,fp);
   }
   fclose (fp);
   fp = fopen ("student1.txt", "r");
   for (i=0; i<2; i++){
      printf ("details of student %d are\n", i+1);
      fread (&s[i], sizeof (s[i]) ,1,fp);
      printf("student number = %d\n", s[i]. sno);
      printf("student name = %s\n", s[i]. sname);
      printf("marks = %f\n", s[i]. marks);
   }
   fclose(fp);
   getch( );
}

Output

When the above program is executed, it produces the following result −

enter details of student 1
student number:1
student name:bhanu
student marks:50
enter details of student 2
student number:2
student name:priya
student marks:69
details of student 1 are
student number = 1
student name = bhanu
marks = 50.000000
details of student 2 are
student number = 2
student name = priya
marks = 69.000000