第6章利用数组处理批量数据(1)汇编

Chapter 6 Arrays
Why arrays
In previous chapters, we have learned basic data types, e.g. int, char, float. In this chapter, we will learn one of the derived data types, called array.
Length is the length of the array and must have a constant value
Why index2nd floor 1st floor 0th ground floor
It is like the building floors, it starts from ground floor (0) to the first floor (1), and then the second (2) floor, so on.
How to use array element
We can array element in any legal expressions (or statement)
int a[10]; int k;
a[k] = expression (has a value)
a[5]= ((x/y+3)%2)*4;
a[0] a[1] a[2] a[3] a[4]
How to define an array
Examples of legal and illegal definitions:
int a[n+6]; (n is a variable)
int _x[10];
int a[k+2]; (k is constant variable) int b[(x>y)+3]; int a[34%3+7];
Array is a group of data that have the same type. E.g. we can define an 8 elements array
int a[8]
Why arrays
Here int indicates that the 8 elements are int types.
We place the 10 number in the array a[10]
And then we print the 10 numbers in the reverse order.
#include <stdio.h> int main() { int i,a[10]; for (i=0; i<=9;i++) a[i]=i; for(i=9;i>=0; i--) Print them in printf("%d ",a[i]); the reverse order printf("\n"); return 0; } a[0]a[1]a[2]a[3]a[4]a[5]a[6]a[7]a[8]a[9] 0 1 2 3 4 5 6 7 8 9
a is the name of the array, and can be other names. 8 is the length of the array, which means there are 8 elements in the array.
Why arrays
The array elements starts from a[0], a[1] ~ a[7] instead of a[1]~a[8].
Assign initial values
int a[ ] ={1,2,3,4,5}; Equivalent to a[5]={1,2,3,4,5};
Store the 10 numbers in array a
Assign initial values
Assign initial values to an array: Int a[5] = {0,1,2,3,4};
Data are separated by comma.
Int a[5] = {0}; Equivalent to int a[5] = {0,0,0,0,0}; When assign values to the a few elements, the remaining elements are assigned 0 automatically.
a[3]=a[7]+a[9];
x=(a[4]*3-1)%2;
y=a[10]/2; ×
How to use array elements
Example, there are ten int numbers, “0,1,
2,3,4,5,6,7,8,9”，we need to print it in the reverse order. Solution:
6.1.1 how to define an array
e.g. define an array of 6 elements int a[5];
Index starts from 0 to 4: they are the 0th element a[0], the 1st element a[1], the 2nd element a[2], the 3rd element a[3], the 4th element a[4].
The number j in a[j] means its distance from the 0th number.
Define an array
In general, we can define array as: type name[length]
type is the type of the array, it can be int, float, char, etc.,, Name is the name of the array