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

High-level I/O functions in C provide an abstracted, user-friendly interface for input and output operations. These functions are part of the standard C library and offer better portability compared to low-level I/O functions.

High Level vs Low Level I/O

High Level I/O

• Easy to understand and use by programmers
• Portable across different systems
• Built-in buffering for better performance

Low Level I/O

• Closer to the operating system
• Faster execution time
• System-dependent (non-portable)

High Level I/O Functions

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

Syntax

fprintf(FILE *stream, const char *format, ...);
fscanf(FILE *stream, const char *format, ...);
int putc(int c, FILE *stream);
int getc(FILE *stream);
int putw(int w, FILE *stream);
int getw(FILE *stream);
int fputs(const char *str, FILE *stream);
char *fgets(char *str, int n, FILE *stream);
size_t fread(void *ptr, size_t size, size_t count, FILE *stream);
size_t fwrite(const void *ptr, size_t size, size_t count, FILE *stream);

Example 1: Using putw() and getw() Functions

The following program stores numbers from 1 to 5 in a file and then reads them back −

#include <stdio.h>

int main() {
    FILE *fp;
    int i, num;
    
    /* Write numbers to file */
    fp = fopen("numbers.txt", "w");
    if (fp == NULL) {
        printf("Error opening file for writing<br>");
        return 1;
    }
    
    for (i = 1; i <= 5; i++) {
        putw(i, fp);
    }
    fclose(fp);
    
    /* Read numbers from file */
    fp = fopen("numbers.txt", "r");
    if (fp == NULL) {
        printf("Error opening file for reading<br>");
        return 1;
    }
    
    printf("File contents: ");
    while ((num = getw(fp)) != EOF) {
        printf("%d ", num);
    }
    printf("<br>");
    
    fclose(fp);
    return 0;
}

Example 2: Using fwrite() and fread() for Structures

This example demonstrates storing and reading student records using binary file operations −

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

struct student {
    int sno;
    char sname[30];
    float marks;
};

int main() {
    struct student s[2];
    FILE *fp;
    int i;
    
    /* Initialize student data */
    s[0].sno = 1;
    strcpy(s[0].sname, "John");
    s[0].marks = 85.5;
    
    s[1].sno = 2;
    strcpy(s[1].sname, "Alice");
    s[1].marks = 92.0;
    
    /* Write to file */
    fp = fopen("student.dat", "wb");
    if (fp == NULL) {
        printf("Error opening file for writing<br>");
        return 1;
    }
    
    for (i = 0; i < 2; i++) {
        fwrite(&s[i], sizeof(struct student), 1, fp);
    }
    fclose(fp);
    
    /* Read from file */
    fp = fopen("student.dat", "rb");
    if (fp == NULL) {
        printf("Error opening file for reading<br>");
        return 1;
    }
    
    printf("Student Records:<br>");
    for (i = 0; i < 2; i++) {
        fread(&s[i], sizeof(struct student), 1, fp);
        printf("Student %d: ID=%d, Name=%s, Marks=%.1f<br>", 
               i+1, s[i].sno, s[i].sname, s[i].marks);
    }
    
    fclose(fp);
    return 0;
}

Key Points

• High-level I/O functions provide buffered I/O operations
• Always check for file opening errors using NULL comparison
• Use fclose() to properly close files and flush buffers
• Binary mode ("rb", "wb") is recommended for structures
• Functions like putw() and getw() are non-standard but widely supported

Conclusion

High-level I/O functions in C provide a portable and efficient way to perform file operations. They handle buffering automatically and offer formatted input/output capabilities, making them ideal for most file handling tasks in C programming.