7 C
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mainSkill
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C
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(Variables) (Address)int a=0;0x0037b000a
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(Variables) (Address)int
a=0;0x0037b000a0x0037b0010x0037b0020x0037b003&a
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(Variables) (Address)int
a=0;0x0037b000a0x0037b0010x0037b0020x0037b003&a
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(Variables) (Address)int
a=0;0x0037b000a0x0037b0010x0037b0020x0037b003&a
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(Variables) (Address)int
a=0;0x0037b000a0x0037b0010x0037b0020x0037b003&a
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Pointer
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Declaring pointersint
a=10;0x0037b000a0x0037b0040x0037b0080x0037b00B&a......100x0037b000
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Declaring pointersint
a=10;0x0037b000a0x0037b0040x0037b0080x0037b00B&a......100x0037b000int
*pa;pa
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Pointer Assignmentsint
a=10;0x0037b000a0x0037b0040x0037b0080x0037b00B&a......100x0037b000int
*pa;pa = &a;int *pa=&a;pa
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Pointer Assignmentsint
a=10;0x0037b000a0x0037b0040x0037b0080x0037b00B&a......100x0037b000int
*pa;pa = &a;int *pa=&a;pa
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Pointer Assignmentsint
a=10;0x0037b000a0x0037b0040x0037b0080x0037b00B&a......100x0037b000int
*pa;pa = &a;int *pa=&a;pa
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int i,*pp=&i; int *p;float *q;p=q;int i;float
*p;p=&i;int *p;p=100;!!
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Dereferencing Pointers and the Address Operatorint i = 24;i is
an int variable&i is like an int pointer, pointing to the
variable ithe Address Operator
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Dereferencing Pointers and the Address Operatorint *p;p =
&i;p is an int pointer *p *p *pthe pointer Operator
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Dereferencing Pointers and the Address Operatorint
a=10;0x0037b000a0x0037b0040x0037b0080x0037b00B&a......200x0037b000int
*pa=&a; *(&a)/*a*/
&(*pa) /*a*/pa
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Using Pointersint
a=10;0x0037b000a0x0037b0040x0037b0080x0037b00B&a......100x0037b000int
*pa;pa = &a;int *pa=&a;*pa = 20;20pa
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Using Pointersint
a=10;0x0037b000a0x0037b0040x0037b0080x0037b00B&a......200x0037b000int
*pa;pa = &a;int *pa=&a;*pa = 20;pa
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int i; scanf("%d", i); /* */
char c; scanf("%d", &c); /* */ii==100100intccint
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Using Pointersint i;int *iPtr = &i;int j = 3;int *jPtr =
&j;
Consider:
*jPtr = *iPtr; i = 4;*jPtr = i;iPtr = j;
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pointer manipulation short *p, a[10]; p = a; p++; pa[0]
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pointer manipulation short *p, a[10]; p = a; p++;
pshortlongpa[0]
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pointer manipulation
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Pointers and ErrorsTo increment a dereferenced pointer, use
(*p)++
rather than
*p++ /* correct but means */
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pointer manipulation 10p > q p < q p == q
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pointer manipulation
main(){ int *p; scanf("%d",p); }main(){ int a,*p=&a;
scanf("%d",p); }TCVC
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Pointers and FunctionsCall by ValueCan not modify the argument
parameter variableCall by Reference In order to modify the argument
use: (Pointer parameter) &(variable)
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void Swap(int *x, int *y) { int temp; temp = *x; *x = *y; *y =
temp; }/* call by reference: int a = 15, b = 8; swap(&a,
&b); */7.1~7.2
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void Swap(int *x, int *y) { int temp; temp = *x; *x = *y; *y =
temp; }/* call by reference: int a = 15, b = 8; int *pa = &a,
*pb = &b; swap(pa, pb); */7.1~7.2
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7.1~7.2
void Swap(int x,int y){ int temp; temp = x; x = y; y =
temp;}
void Swap(int *x,int *y){ int temp; temp = *x; *x = *y; *y =
temp;}
main(){ int a, b; a = 5; b = 9; Swap( &a, &b );
printf("a=%d,b=%d",a,b);} main(){ int a, b; a = 5; b = 9; Swap(a,
b); printf("a=%d,b=%d",a,b);} 1 2 Trace the execution
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main(){ int a, b; a = 5; b = 9; Swap(a, b);
printf("a=%d,b=%d",a,b);}void Swap(int x, int y){ int temp; temp =
x; x = y; y = temp;}55ab 99 1xy55temp9x y
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main(){ int a, b; a = 5; b = 9; Swap(&a, &b);
printf("a=%d,b=%d",a,b);}void Swap(int *x, int *y){ int temp; temp
= *x; *x = *y; *y = temp;}&a&a &b&b
2xy5temp5ab995*x*yx y
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void Swap(int *x, int *y){ int temp;
temp = *x; *x = *y; *y = temp;}pTemppTempvoid Swap(int *x, int
*y){ int *pTemp; *pTemp = *x; *x = *y; *y = *pTemp;}
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void Swap(int *x, int *y){ int temp;
temp = *x; *x = *y; *y = temp;}void Swap(int *x, int *y){ int
*pTemp; pTemp = x; x = y; y = pTemp;}
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7.5~7.6
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C''"Hello China"pStr'\0'
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char *pStr = "Hello China";"Hello China"pStrchar str[12] =
{"Hello China"}; char *pStr;pStr = "Hello China";strpStr =
&str[0];
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str = "Hello China";"Hello China"pStrchar str[12] = {"Hello
China"}; char *pStr;pStr = "Hello China";strstr pStr
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7.5 void MyStrcpy(char dstStr[], char srcStr[]){int i = 0; while
(srcStr[i] != '\0'){ dstStr[i] = srcStr[i]; i++; }dstStr[i] =
'\0';}srcStr[i]dstStr[i]Hi=0ei=1li=2li=3oi=4i=5Ci=6hi=7ii=8ni=9ai=10\0srcStr[i]=='\0
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7.5 void MyStrcpy(char *dstStr, char *srcStr){while (*srcStr !=
'\0'){ *dstStr = *srcStr; srcStr++; dstStr++; }*dstStr = '\0';
}*srcStr*dstStrHelloChina\0*srcStr=='\0srcStr++dstStr++
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7.5 void MyStrcpy(char *dstStr, const char *srcStr){while
(*srcStr != '\0'){ *dstStr = *srcStr; srcStr++; dstStr++; }*dstStr
= '\0'; }*srcStr*dstStrHellChina\0oconst Protecting Parameter
Values
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A const qualifier qualify pointersconst const int *p; pointer to
a constant integerp the value of p may change, but the value of *p
can not*p = 10VC error C2166: l-value specifies const objectint
*const p; constant pointer to integerpthe value of *p can change,
but the value of p can not
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7.6 unsigned int MyStrlen(char str[]){ int i;unsigned int len =
0; for (i=0; str[i]!='\0'; i++) {len++; }return (len);}
unsigned int MyStrlen(const char *pStr){ unsigned int len = 0;
for (; *pStr!='\0'; pStr++) {len++; }return (len); }
21
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int
a[4]={1,2,3,4};0x0037b000a[0]0x0037b0040x0037b0080x0037b00Ba....1int
*pa=a;paint *pa=&a[0];234a[1]a[2]a[3]
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int
a[4]={1,2,3,4};0x0037b000a[0]0x0037b0040x0037b0080x0037b00Ba....1int
*pa=a;paint
*pa=&a[0];234a[1]a[2]a[3]a[i]*(a+i)pa[i]*(pa+i)a+1*(a+1)pa[0]*(pa+2)pa+2*pa
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int
a[4]={1,2,3,4};0x0037b000a[0]0x0037b0040x0037b0080x0037b00Ba....1p234a[1]a[2]a[3]for
(i=0; i
