代码 1
m = &count;
代码 2
q = *m;
代码 3
#include <stdio.h>
int main(void)
{
int x = 99;
int *p1, *p2; //定义指针变量
p1 = &x;
p2 = p1;
/* print the value of x twice */
printf("Values at p1 and p2: %d %d\n", *p1, *p2);
/* print the address of x twice */
printf("Addresses pointed to by p1 and p2: %p %p", p1, p2); //打印出指针
return 0;
}
代码 4
#include <stdio.h>
int main(void)
{
double x = 100.1, y;
int *p;
/* The next statement causes p (which is an integer pointer) to point to a double. */
p = (int *) &x;
/* The next statement does not operate as expected. */
y = *p; /* attempt to assign y the value x through p */
/* The following statement won't output 100.1. */
printf("The (incorrect) value of x is: %f", y);
return 0;
}
代码 5
p1++;
代码 6
p1--;
代码 7
p1 = p1 + 12;
代码 8
if(p < q)
printf("p points to lower memory than q\n");
代码 9 入栈 出栈
#include <stdio.h>
#include <stdlib.h>
#define SIZE 10
void push(int i);
int pop(void);
int *tos, *p1, stack[SIZE];
int main(void)
{
int value;
tos = stack; /* tos points to the top of stack */
p1 = stack; /* initialize p1 */
do {
printf("Enter value: ");
scanf("%d", &value);
if(value != 0) push(value);
else printf("value on top is %d\n", pop());
} while(value != -1);
return 0;
}
void push(int i)
{
p1++;
if(p1 == (tos+SIZE)) {
printf("Stack Overflow.\n");
exit(1);
}
*p1 = i;
}
int pop(void)
{
if(p1 == tos) {
printf("Stack Underflow.\n");
exit(1);
}
p1--;
return *(p1+1);
}
代码 10
return *p1+1;
代码 11
char str[80], *p1;
p1 = str;
代码 12
str[4]
代码 14
/* Index s as an array. */
void putstr(char *s)
{
register int t;
for(t=0; s[t]; ++t) putchar(s[t]);
}
/* Access s as a pointer. */
void putstr(char *s)
{
while(*s) putchar(*s++);
}
代码 15
int *x[10];
代码 16
x[2] = &var;
代码 17
*x[2]
代码 18
void display_array(int *q[])
{
int t;
for(t=0; t<10; t++)
printf("%d ", *q[t]);
}
代码 19
void syntax_error(int num)
{
static char *err[] = {
"Cannot Open File\n",
"Read Error\n",
"Write Error\n",
"Media Failure\n"
};
printf("%s", err[num]);
}
代码 20
float **newbalance;
代码 21
#include <stdio.h>
int main(void)
{
int x, *p, **q;
x = 10;
p = &x;
q = &p;
printf("%d", **q); /* print the value of x */
return 0;
}
代码 22
char *p = 0;
代码 23
p = NULL;
代码 24
int *p = 0;
*p = 10; /* wrong! */
代码 25
#include <stdio.h>
#include <string.h>
int search(char *p[], char *name);
char *names[] = {
"Herb",
"Rex",
"Dennis",
"John",
NULL}; /* null pointer constant ends the list */
int main(void)
{
if(search(names, "Dennis") != -1)
printf("Dennis is in list.\n");
if(search(names, "Bill") == -1)
printf("Bill not found.\n");
return 0;
}
/* Look up a name. */
int search(char *p[], char *name)
{
register int t;
for(t=0; p[t]; ++t)
if(!strcmp(p[t], name)) return t;
return -1; /* not found */
}
代码 26
char *p = "hello world";
代码 27
#include <stdio.h>
#include <string.h>
char *p = "hello world";
int main(void)
{
register int t;
/* print the string forward and backwards */
printf(p,"\n");
for(t=strlen(p)-1; t>-1; t--)
printf("%c\n", p[t]);
return 0;
}
代码 28
#include <stdio.h>
#include <string.h>
void check(char *a, char *b,
int (*cmp)(const char *, const char *));
int main(void)
{
char s1[80], s2[80];
int (*p)(const char *, const char *); /* function pointer */
p = strcmp; /* assign address of strcmp to p */
printf("Enter two strings.\n");
gets(s1);
gets(s2);
check(s1, s2, p); /* pass address of strcmp via p */
return 0;
}
void check(char *a, char *b,
int (*cmp)(const char *, const char *))
{
printf("Testing for equality.\n");
if(!(*cmp)(a, b)) printf("Equal");
else printf("Not Equal");
}
代码 29
(*cmp)(a, b)
代码 30
cmp(a, b);
代码 31
check(s1, s2, strcmp);
代码 32
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
void check(char *a, char *b,
int (*cmp)(const char *, const char *));
int compvalues(const char *a, const char *b);
int main(void)
{
char s1[80], s2[80];
printf("Enter two values or two strings.\n");
gets(s1);
gets(s2);
if(isdigit(*s1)) {
printf("Testing values for equality.\n");
check(s1, s2, compvalues);
}
else {
printf("Testing strings for equality.\n");
check(s1, s2, strcmp);
}
return 0;
}
void check(char *a, char *b,
int (*cmp)(const char *, const char *))
{
if(!(*cmp)(a, b)) printf("Equal");
else printf("Not Equal");
}
int compvalues(const char *a, const char *b)
{
if(atoi(a)==atoi(b)) return 0;
else return 1;
}
代码 33
char *p;
p = malloc(1000); /* get 1000 bytes */
代码 34
int *p;
p = malloc(50*sizeof(int));
代码 35
p = malloc(100);
if(!p) {
printf("Out of memory.\n");
exit(1);
}
代码 36
/* Allocate space for a string dynamically, request user
input, and then print the string backwards. */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
char *s;
register int t;
s = malloc(80);
if(!s) {
printf("Memory request failed.\n");
exit(1);
}
gets(s);
for(t=strlen(s)-1; t>=0; t--) putchar(s[t]);
free(s);
return 0;
}
代码 37
#include <stdio.h>
#include <stdlib.h>
int pwr(int a, int b);
int main(void)
{
/* Declare a pointer to an array that has 10
ints in each row. */
int (*p)[10];
register int i, j;
/* allocate memory to hold a 4 x 10 array */
p = malloc(40*sizeof(int));
if(!p) {
printf("Memory request failed.\n");
exit(1);
}
for(j=1; j<11; j++)
for(i=1; i<5; i++) p[i-1][j-1] = pwr(j, i);
for(j=1; j<11; j++) {
for(i=1; i<5; i++) printf("%10d ", p[i-1][j-1]);
printf("\n");
}
return 0;
}
/* Raise an integer to the specified power. */
pwr(int a, int b)
{
register int t=1;
for(; b; b--) t = t*a;
return t;
}
代码 38
p = (int (*)[10]) malloc(40*sizeof(int));
代码 39
/* This program is wrong. */
int main(void)
{
int x, *p;
x = 10;
*p = x; /* error, p not initialized */
return 0;
}
代码 40
/* This program is wrong. */
#include <stdio.h>
int main(void)
{
int x, *p;
x = 10;
p = x;
printf("%d", *p);
return 0;
}
代码 41
p = x;
代码 42
p = &x;
代码 43
char s[80], y[80];
char *p1, *p2;
p1 = s;
p2 = y;
if(p1 < p2) . . .
代码 44
int first[10], second[10];
int *p, t;
p = first;
for(t=0; t<20; ++t) *p++ = t;
代码 45
/* This program has a bug. */
#include <string.h>
#include <stdio.h>
int main(void)
{
char *p1;
char s[80];
p1 = s;
do {
gets(s); /* read a string */
/* print the decimal equivalent of each
character */
while(*p1) printf(" %d", *p1++);
} while(strcmp(s, "done"));
return 0;
}
代码 46
/* This program is now correct. */
#include <string.h>
#include <stdio.h>
int main(void)
{
char *p1;
char s[80];
do {
p1 = s; /* reset p1 to beginning of s */
gets(s); /* read a string */
/* print the decimal equivalent of each
character */
while(*p1) printf(" %d", *p1++);
} while(strcmp(s, "done"));
return 0;
}
