program bug

I have looked this program up and down and I don't see what's wrong with
it. But it always breaks and gives me an error "mode error" no matter which
mode binary or text I choose. This simple program is supposed to take as
argv[1] a "b" or "t" for binary or text. It's not taking anything.

#include <stdio.h>

int main(int argc, char **argv) {
char *b;
int a;
FILE *ifp,*ofp;
if (argc!=4) {
fprintf(stderr,"usage error\n");
return -1;
}
if (argv[1]=="b") {
b="rb";
}
if (argv[1]=="t") {
b="rt";
}
if (argv[1]!="t"||argv[1]!="b") {
fprintf(stderr,"mode error\n");
return -1;
}
if ((ifp=fopen(argv[2],b))==0) {
fprintf(stderr,"open error i\n");
return -1;
}
if ((ofp=fopen(argv[3],b))==0) {
fprintf(stderr,"open error o\n");
return -1;
}
while(a!=EOF)
a=fgetc(ifp);
fputc(a,ofp);
printf("done\n");
return 0;}

Is anyone good enough to glance at this and see what's wrong?

Bill


.

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