File Streams in Standard C

File input and output in C utilizes the standard FILE* stream handle from <stdio.h>. Always verify that fopen() returns a non-null pointer before attempting read/write operations.

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C Source Code: Text & Binary File Operations

c (ISO Standard)
Run in Compiler.cCopy
#include <stdio.h>
#include <stdlib.h>

typedef struct {
    int id;
    char name[32];
    double score;
} StudentRecord;

int main() {
    const char *filename = "students.dat";

    /* 1. Write binary records to file */
    FILE *outFile = fopen(filename, "wb");
    if (!outFile) {
        perror("Failed to open file for writing");
        return EXIT_FAILURE;
    }

    StudentRecord s1 = {101, "Alice Smith", 94.5};
    StudentRecord s2 = {102, "Bob Johnson", 88.0};

    fwrite(&s1, sizeof(StudentRecord), 1, outFile);
    fwrite(&s2, sizeof(StudentRecord), 1, outFile);
    fclose(outFile);
    printf("Binary records successfully written to %s.\n", filename);

    /* 2. Read binary records back from file */
    FILE *inFile = fopen(filename, "rb");
    if (!inFile) {
        perror("Failed to open file for reading");
        return EXIT_FAILURE;
    }

    StudentRecord reader;
    printf("\nReading binary records from disk:\n");
    while (fread(&reader, sizeof(StudentRecord), 1, inFile) == 1) {
        printf("  ID: %d | Name: %-12s | Score: %.1f\n", reader.id, reader.name, reader.score);
    }

    fclose(inFile);
    remove(filename); /* Clean up temporary file */
    return EXIT_SUCCESS;
}

Sample Output

text (ISO Standard)
Copy
Binary records successfully written to students.dat.

Reading binary records from disk:
  ID: 101 | Name: Alice Smith  | Score: 94.5
  ID: 102 | Name: Bob Johnson  | Score: 88.0

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Complexity Analysis

• Time Complexity: $O(filesize)$ bounded by disk I/O throughput.
• Space Complexity: O(1) fixed memory struct buffer.

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Related Guides

• Comprehensive tutorial in File Handling in C.
• Record modeling with structs in Structures in C.