C language Misunderstanding

On the study of C language, I think there are some misunderstandings in the pointer and array. In the free time to write a little personal experience, I feel that writing is not very good, just a small personal experience, write bad, but also please master forgive me, pointing under the misunderstanding, contact [email protected],

Also hope that you master enlighten.

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All variables in the C language are memory, and defining variables is requesting memory

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1. String

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1. The string is in memory in the form of a character array, ending with '/', Length: number of characters +1;

String in the operation: the first address assigned to the address, take the string is not required * (for example: Char *p= "gght"; printf ("%s", p);), but need to add * when taking characters;

String operation Loop End flag: Judge p[i]== ' + '; or strlen (p);

sizeof (p)/sizeof (p[0])----> capacity

sizeof calculates the total size of the entire array

Strlen calculates the size of the string itself without '

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2. Arrays and pointers

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1. Pointers and other types of swaps: both address

A.int A; int *p; p=&a;

B.int A[3]; int (*p) [3]; p=&a;

C.int *a[3]; int * (*A) [3]; p=&a;

2. Array operations are treated as pointers, first addresses and operations

3. Array length: char a[]; sizeof (a)/siaeof (A[0])-1;

4. Array and pointer operations:

Such as:

int a[3]; | int a[3];

int *p; | int *p[3];

P=a; | p=&a;

a[i]=* (p+i); |

Pointer and array operations: divided into two parts: the 2nd part of the same is taken: the first address

The 2nd part is different, take: &: Entire address

sizeof () of the pointer = 4; As long as the pointer is the constant theorem

<5>. Flexible use of arrays:

char * a[]: Divided into two parts: 1:a[]; 2:char*;

Char a[]: divided into two parts: 1:a[]; 2:char;

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3. Complex statement Reading

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How to read: Find the first non-key character and peel the Onion as he centers

such as: void (* Signed (Signed, Void (*p) int)) int

typedef tmp VOID (*) int

TMP signed (signed, TMP p)

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4. Data type

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1. Redefine:

typedef long int32_t; Define int32_t as Long 4 bytes

typedef short INT32_4 defines int32_t as short 4 bytes

int 4 bytes, char 1 bytes, short 2 bytes, long 4 bytes;

Double:%lf float:%f;

2. Force type conversions:

such as: int p;

(char) p; int--->char

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5. Memory

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OS------> operating system

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Stack------> Local variables, formal parameters (after the function runs, memory is released)

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Heap------>malloc (), Calloc (), realloc () allocate memory, must be in conjunction with free ()

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Data segment----> global variables, static variables (memory is not freed after function run ends)

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6. Commissioning

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#ifdef x;

printf ("..", x);

#enif

Debug partial compile time: gcc--. c-o. -DX only works.

----------------------------------> completed on: March 10, 2015

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C language Misunderstanding