#include #include #include #define MAXBUFFERSIZE 80 char convertChar(char ch) { if(isupper(ch) != 0) { ch = tolower(ch); } else { ch = toupper(ch); } return ch; } int main(int argc, char *argv[]) { char buffer[MAXBUFFERSIZE]; int i; strcpy(buffer, argv[1]); for(i = 0; i < strlen(buffer); i++) { buffer[i] = convertChar(buffer[i]); } /* buffer[charCount] = 0x00; null terminating */ printf("%s\n", buffer); }