We learnpointerWhen there may be a lot of things so that we confuse so I use a few small experimental program to give you answers to your questions：
First, from the definition, the variable is a pointer to the address stored in the variable。
Unary operator * is the indirection or dereference operator
Unary operator&Take for an object address，It can only be applied to objects in memory
That * (indirection get is a specific value stored in memory)
For pointers experiment
Experiment one
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[root@localhost ~]# vim zhizhenshiyan1.c #include<stdio.h> main(void) { int x=1; int *ip; ip=&x; printf("十进制显示d ip=%d\n",ip); printf("十进制显示d *ip=%d\n",*ip); printf("二进制显示x ip=%x\n",ip); printf("二进制显示x *ip=%x\n",*ip); } |
The results compiled to
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[root@localhost ~]# ./a.out 十进制显示d ip=928094692 十进制显示d *ip=1 二进制显示x ip=375199e4 二进制显示x *ip=1 |
A pointer is a variable that holds the address of the variable，In Experiment 1，
ip=&x;
ip address pointing to x to x ip
We will address assigned to the variable x ip
I'm just learning this time in this place is not very deep understanding so there is a test
From the experiments, we can know the difference between a direct addressing and indirect addressing of，I, respectively, in decimal and binary print direct addressing and indirect addressing values，
Direct addressing is printed x address information in memory，Data obtained is directly addressing an address
The indirect addressing is set up on the basis of the direct addressing，Objects Introduction Addressing a value corresponding to the address stored in。
Experiment two
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#include<stdio.h> main(void) { int x=1 , y=2; int *ip; printf("int x=1 , y=2;\nint *ip\n"); ip = &x; printf("ip=&x=%d\n",ip); y = *ip; printf("y=*ip=%d\n",y); *ip = 0; printf("*ip=0 x=%d\n",x); printf("&x=%d",&x); } |
———————————————-
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[root@localhost ~]# ./a.out int x=1 , y=2; int *ip ip=&x=1226821388 y=*ip=1 *ip=0 x=0 &x=1226821388 |
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The second experiment we can get the following information
First pointer is a variable,Can be changed。
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int x=1 , y=2; *ip=0; printf("*ip=0 x=%d\n",x); printf("&x=%d",&x); |
This tells us a few lines of code to change the assignment of indirect addressing is the address of an object。Before and after the two directly addressed&x The output can be learned
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Third experiment
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#include<stdio.h> main(void) { int z; int x=1 , y=2 ; char a='!' , b='#' ; int *ip , *ab; char *c ,*d; ip = &x; ab = &y; printf("int z\nint x=1,y=2\nint *ip,*ab;\n*ip=&x *ab=&y\n"); *ip=*ip+10; printf("*ip=*ip+10=%d\n",*ip); z = *ip + *ab; printf("z=*ip+*ab=%d\n",z); } |
The compiled results
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[root@localhost ~]# ./a.out int z int x=1,y=2 int *ip,*ab; *ip=&x *ab=&y *ip=*ip+10=11 z=*ip+*ab=13 |
Indirect addressing is the value obtained，Their operation is the value of the arithmetic /
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Experiment 4
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#include<stdio.h> main(void) { char x=1 , y=2; char *ip; ip=&x; *ip=123; printf("%c",*ip); } |
Results after running
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[root@localhost ~]# ./a.out { |
In asc code 123 is represented by the symbol”{“
This experiment is very simple to tell us the direct and indirect references cited various relationships，Is a direct reference to the value of the address stored reference value (coding addresses) in asc code 123 is represented by the symbol{Therefore, the output * ip direct reference number 123 the storage location when the represents the symbol”{“.
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ps:In 32-bit systems can use int value pointer value can be expressed even unary mutual，Especially referring asc code
Original article written by LogStudio：R0uter's Blog » About pointers in c language in some of the experiments
Reproduced Please keep the source and description link：https://www.logcg.com/archives/286.html
