The C programming language (second edition,KR) exercise（CHAPTER 7）

     $Excercise7-1$：

#include <stdio.h>
#include <string.h>
#include <ctype.h>enum type { LOWER, UPPER };int main(int argc, char *argv[])
{int c, mode = -1;if (stricmp(*argv, "lower.exe") == 0) {printf("To lower\n");mode = LOWER;		}else if (stricmp(*argv, "upper.exe") == 0) {printf("To upper\n");mode = UPPER;	}		if (mode == LOWER){while ((c = getchar()) != EOF)putchar(tolower(c));		}else if (mode == UPPER){while ((c = getchar()) != EOF)putchar(toupper(c));		}return 0;
}

     $Excercise7-2$：

#include <stdio.h>
#include <ctype.h>/* "%x" for hex, "%o" for octal */ 
#define FORMAT "%x" 
#define LINELEN 75int main()
{int c, i = 0;while ((c = getchar()) != EOF){/* reset line length counter */ if (c == '\n') i = 0;/* check if equal to line length. If so, print new line and reset counter */ 	else if (++i == LINELEN) {i = 0;putchar('\n');}/* graphic characters and spaces */ if (isgraph(c) || isspace(c)) {putchar(c);			}else{/* non-graphic characters */printf(FORMAT, c);  			}}return 0;
}

     $Excercise7-3$：

#include <stdio.h>
#include <stdarg.h>void minprintf(char *fmt, ...);int main()
{char *sval = "10";int ival = 11;double dval = 12.13;unsigned int uival = 14;char cval = 'F';void *pval = sval;minprintf("%%s=%s, %%d=%d, %%i=%i, %%f=%f, %%e=%e, %%E=%E, %%g=%g, %%G=%G, %%o=%o, %%x=%x\n", sval, ival, ival, dval, dval, dval, dval, dval, uival, uival);printf("%%s=%s, %%d=%d, %%i=%i, %%f=%f, %%e=%e, %%E=%E, %%g=%g, %%G=%G, %%o=%o, %%x=%x\n", sval, ival, ival, dval, dval, dval, dval, dval, uival, uival);minprintf("%%X=%X, %%u=%u, %%c=%c, %%p=%p, %%%%=%%\n", uival, uival, cval, pval);printf("%%X=%X, %%u=%u, %%c=%c, %%p=%p, %%%%=%%\n", uival, uival, cval, pval);
}/* minimal printf with variable argument list */ 
void minprintf(char *fmt, ...)
{/* points to each unnamed arg in turn */ va_list ap; char *p, *sval, format[3] = { '%', '\0', '\0' };int ival;double dval;unsigned int uival;void *pval;/* make ap point to 1st unnamed arg */ va_start(ap, fmt); for (p = fmt; *p; p++){if (*p != '%'){putchar(*p);continue;}switch (*++p){case 'd': case 'i': case 'c': /* char is promoted to int when passed through '...' */ ival = va_arg(ap, int);format[1] = *p;printf(format, ival);break;case 'f': case 'e': case 'E': case 'g': case 'G':dval = va_arg(ap, double);format[1] = *p;printf(format, dval);break;case 's':for (sval = va_arg(ap, char *); *sval; sval++)putchar(*sval);break;case 'x': case 'X': case 'o':  case 'u':uival = va_arg(ap,<