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The C Users' Group Library 1994 August
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wc-cdrom-cusersgrouplibrary-1994-08.iso
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vol_200
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253_01
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uplow.c
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1990-02-14
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/* Chapter 13 - Program 1 */
#include "STDIO.H"
#include "ctype.h" /* Note - your compiler may not need this */
void mix_up_the_chars(char line[]);
void main()
{
FILE *fp;
char line[80], filename[24];
char *c;
printf("Enter filename -> ");
scanf("%s",filename);
fp = fopen(filename,"r");
do {
c = fgets(line,80,fp); /* get a line of text */
if (c != NULL) {
mix_up_the_chars(line);
}
} while (c != NULL);
fclose(fp);
}
void mix_up_the_chars(char line[])
/* This function turns all upper case
characters into lower case, and all
lower case to upper case. It ignores
all other characters. */
{
int index;
for (index = 0;line[index] != 0;index++) {
if (isupper(line[index])) /* 1 if upper case */
line[index] = tolower(line[index]);
else {
if (islower(line[index])) /* 1 if lower case */
line[index] = toupper(line[index]);
}
}
printf("%s",line);
}
/* Result of execution
(The selected file is displayed on the monitor with all of
the upper case characters converted to lower case, and all
of the lower case characters converted to upper case.)
*/