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Pointer

Introduction to this section:

In the previous section we resolved the arrays in the C language composite data type, in this section we will

Focus, C language Soul-----pointers to learn! The advantage of using pointers: using pointers to represent and use complex data structures;

More convenient use of our arrays and strings; You can handle memory cell addresses directly as assembly language, and you can dynamically make memory space

allocation, C language pointer is the focus, but also the difficulty of C, let everyone follow the footsteps of the author, c in the hands of the analysis of the!

Learning Roadmap for this section:

pointer concepts, pointers vs. one-dimensional arrays and strings:

pointers and two-dimensional arrays:

This knowledge point is a pointer to the difficulty, in fact, to understand here, we just put the center of gravity on the two-dimensional array, the two-dimensional array to thoroughly understand!

Step 1: two-dimensional arrays store data in rows and columns; we can look at a number of lines + one-dimensional array of several columns per row

int a[3][4] ={{1,2,3,4},{1,2,3,4},{1,2,3,4}}; Can be viewed as three rows with four one-dimensional arrays per row

Step 2:a represents the address of the first element of a two-dimensional array, that is, &a[0], if the second and three lines of the newline array are only required : A + 1,a+2 ; &a[1],&a[2]

Step 3: We can think of a[0] as a pointer to a[0][0] , then a[0]+1 points to A[0][1], that is, the address at this time is &A[0][1]

PS: +1 of the 1 here is the number of bytes of the array elements, such as int a[], then this + 1 means to move backwards 4 bytes, pointing to the next element;

If it's +2, it's 8 bytes behind, so a[i][2] = A[i] + 2

Step 4: Through the previous one-dimensional array learning, we can know A[i] and * (a+i) equivalent

Similarly, we extend to a two-dimensional array of cases A[i][j] and * (a+i) +j and a[i]+j are equivalent, both represent A[I][J] addresses

the value of A[i][j] : * (A[I]+J) and * (* (a+i) +j) are OK

Note :*a and * (a+i) do not represent any specific array elements, so you may cause errors when quoting them!

① Array First address a[0]: A can not be directly referenced !!!

② one-dimensional array a[0] The address of the first dollar (&a[0][0]): a[0],* (a+0), *a;

③ First line address: A + 1 also cannot be applied directly

④ one-dimensional array a[1] The address of the first dollar (&a[1][1]): a[1],* (A + 1)

⑤ number 2 row 4 column element a[2][4] address:a[2]+4,* (a+2) +4,a[2][4]

code example:

① points to an array element:

Run:

② pointing to an array

Run:

Summary:

① pointer concept, pointer variable, direct access and indirect access

Basic use of ② pointers

③ pointers and one-dimensional arrays

④ Pointers and strings

⑤ pointers and two-dimensional arrays

This paper draws on: http://blog.csdn.net/coder_pig/article/details/37754625

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C (5)