ISO C90错误：声明

Question

首先让我说，这个标准是必需的，是我目前使用的。

不管怎么说，我得到一个错误，并试图在所有移动我的FILE *块，内/外主，可执行文件之前，等等

#include <stdio.h> 
#include <stdlib.h> 

/* Initialize vars */ 
char c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12; 

int main() 
{ 

    /* Open encrypted.txt for reading */ 
FILE *enc; 
enc = fopen("encrypted.txt", "r"); 

    /* Retrieve individual characters, displace by 4 letters (decryption method) */ 
c1 = (getc(enc))-4; 
c2 = (getc(enc))-4; 
c3 = (getc(enc))-4; 
c4 = (getc(enc))-4; 
c5 = (getc(enc))-4; 
c6 = (getc(enc))-4; 
c7 = (getc(enc))-4; 
c8 = (getc(enc))-4; 
c9 = (getc(enc))-4; 
c10 = (getc(enc))-4; 
c11 = (getc(enc))-4; 
c12 = (getc(enc))-4; 

    /* Display resulting decrypted message */ 
printf("%c%c%c%c%c%c%c%c%c%c%c%c", (char)c1, (char)c2, (char)c3, (char)c4, (char)c5, (char)c6, (char)c7, (char)c8, (char)c9, (char)c10, (char)c11, (char)c12); 

    /* Write decrypted message to new file named "decrypted" */ 
FILE *dec; 
dec = fopen("decrypted", "w"); 

fprintf(dec,"%c%c%c%c%c%c%c%c%c%c%c%c", (char)c1, (char)c2, (char)c3, (char)c4, (char)c5, (char)c6, (char)c7, (char)c8, (char)c9, (char)c10, (char)c11, (char)c12); 

    /* Close files */ 
fclose(enc); 
fclose(dec); 

} 

如何摆脱这种错误的任何提示赞赏！在此先感谢

Answer 1

C90不以块等语句后允许变量声明，所以你需要在顶部声明十二月一起在这里你声明ENC：

int main() 
{ 

    /* Open encrypted.txt for reading */ 
    FILE *enc, *dec; 
    ... 
} 

Answer 2

在C99，你可以等以后申报语句和内部for循环。但不是在C90中

如果使用gcc，请使用-std = c99选项来避免此错误。

gcc -std=c99 -Wall source.c 

或者

移动FILE *dec;到FILE *enc;

下像这种

FILE *enc; 
FILE *dec;