C Programming tips

I have been learning the C language for N years, but I found that there are always some small places I will forget... just remember it!

2012.12.26

# Include <stdio. h> void main (void) {char ptr1 [] = "pear"; // String Array char * prt2 = "orange"; // define a pointer, point to the string char * ptr3 [2] = {"apple", "banner"}; // define the pointer array, pointing to two different strings respectively, char * prt2 upgraded char (* ptr4) [3] = {"Watermelon"}; // defines a pointer pointing to a string with a length of 2 characters, it is a char * prt2 upgrade printf ("ptr1: % s \ n", ptr1); // display the ptr1 String Array printf ("ptr1: % c \ n ", ptr1 [2]); // display the third character printf ("ptr2: % s \ n", prt2) of the ptr1 string array ); // display the ptr2 string pointer to the string printf ("ptr2: % s \ n", prt2 + 2 );// Display (ptr2 string pointer + 2) to the string printf ("ptr2: % c \ n", * (prt2 + 2); // display (ptr2 string pointer + 2) printf ("ptr3 [0]: % s \ n", ptr3 [0]); // display a string as long as the first address is given in the Variable. printf ("ptr3 [0]: % d \ n", ptr3 [0]); // display the value of printf ("ptr4: % s \ n", ptr4); printf ("ptr4 [0]: % s \ n ", ptr4 [0]); // display the entire ptr4 string printf (" ptr4 [1]: % s \ n ", ptr4 [1]); // display the string printf after ptr4 starts from 1*3 ("ptr4 [2]: % s \ n", ptr4 [2]); // display the strings following ptr4 starting from 2*3 // The following lines. ptr1 [2] is a variable, so you can assign values. * (prt2 + 2) is part of a String constant. And cannot be assigned a value. Ptr1 [2] = 'D'; printf ("ptr1: % c \ n", ptr1 [2]); // * (prt2 + 2) = 'D '; // printf ("ptr2: % c \ n", * (prt2 + 2); // char * p is a pointer and no memory is allocated, the "abc123ABC" he points to is read-only and cannot be changed. You must assign a value to him below. // char p [] is an array with allocated memory, is to copy "abc123ABC" to the memory, the memory is read/write // You just need to remember, the pointer is not allocated memory, it points to the system read-only memory, therefore, the read-only // array allocates memory, that is, copying the value in the system's read-only memory to its memory. Therefore, you can use a pointer to read/write a character string, when displaying characters, the pointer must be used to point to the content. // ptr1 is a numerical name and a pointer to an array. ptr1 [0] is the content, & ptr1 [0] is a pointer to ptr1 [0 .}

PS:

Char (* ptr3) [2] = {"apple", "banner "};
Warning C4047: 'initializing': 'Char (*) [2] 'differs in levels of indirection from 'Char [6]'
Error C2078: too initialize initializers
Because char (* ptr3) [2] is essentially the same as char (* ptr3), it only uses [2] to control the length of each pointer string.