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Understanding Function Usage and File Operations in C Programming

This guide explores the fundamentals of function definitions and file operations in C programming. The sections cover how to declare functions, handle parameters, and return values effectively. It also discusses using the `fopen`, `fscanf`, and `fprintf` functions to read from and write to files, demonstrating these concepts through practical code examples. Understanding this material requires a basic grasp of C syntax and file handling procedures, which are crucial for managing input and output in various applications.

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Understanding Function Usage and File Operations in C Programming

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  1. Function and fopen(2)

  2. function • 語法 • 傳回值型態 函數名稱(參數傳遞) 參數傳遞型態 { 函數的主体 }

  3. function #include <stdio.h> main () { void example( ); example( ); } Void example( ) { printf(“ this is a function program!\n”); } Execute 完後回去

  4. #include <stdio.h> int sum (int x ,int y) { int z; : return (z); } void main(){ int a,b,c; : c=sum (a,b); : }

  5. Program-Controlled Input and Output Files • declare a file pointer variable • FILE *inp , /* pointer to input file */ • *outp ; /* pointer to output file */ • the calls to function fopen • inp = fopen(“b:distance.dat”, “r” ) ; • outp = fopen(“b:distance.out”, “w”) ; • use of the functions • fscanf(inp, “%lf”, &miles); • fprintf(outp, “The distance in miles is %.2f. \n”, miles); • end of use • fclose(inp); • fclose(outp);

  6. An example #include <stdio.h> int main(void) { int age; FILE *inp,*outp; inp=fopen("a1.dat","r"); outp=fopen("a2.out","w"); fscanf(inp,"%d",&age); fprintf(outp,"that is %d",age); fclose(inp); fclose(outp); } 必須要有a1.dat這一個檔案.來提供來源!~~ 從這讀進入 A1.dat 寫到這一個檔案 A2.out 必須關閉檔案

  7. ? • 有什麼問題?

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