YouTipC Pointer to an Array |
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C Pointer to an Array
You can skip this chapter first and come back to learn its content after you understand the concept of C pointers.
If you have some understanding of the concept of pointers in C language, then you can start learning this chapter.
The array name itself is a constant pointer, meaning its value cannot be changed. Once determined, it cannot point elsewhere.
Therefore, in the following declaration:
double balance;
balance is a pointer to &balance, which is the address of the first element of the array balance. Therefore, the following code snippet assigns p the address of the first element of balance:
double *p;
double balance;
p = balance;
Using the array name as a constant pointer is legal, and vice versa. Therefore, *(balance + 4) is a valid way to access the data in balance.
Once you store the address of the first element in p, you can use *p, *(p+1), *(p+2), etc., to access the array elements. The following example demonstrates these concepts discussed above:
Example
#include<stdio.h>
int main()
{
/* An integer array with 5 elements */
double balance = {1000.0, 2.0, 3.4, 17.0, 50.0};
double *p;
int i;
p = balance;
/* Output each element's value */
printf("Array values using pointern");
for ( i = 0; i < 5; i++ )
{
printf("*(p + %d) : %fn", i, *(p + i));
}
printf("Array values using balance as addressn");
for ( i = 0; i < 5; i++ )
{
printf("*(balance + %d) : %fn", i, *(balance + i));
}
return 0;
}
When the above code is compiled and executed, it produces the following result:
In the above example, p is a pointer to a double, which means it can store the address of a double variable. Once we have the address in p, *p will give the value stored at the corresponding address in p, as demonstrated in the example above.
2 Notes
#0 tuingke
142***2460@qq.com
About the double type and float type:
printf() only sees double-precision numbers. The %f format specifier for printf always yields a double. Therefore, using %f or %lf in printf() produces the same output display. However, for variables, the double type has higher precision than the float type. "Higher precision" for double means it stores more decimal places, but the default output is 6 decimal places. If you want to output more decimal places, you can control it yourself, for example, %.10lf will output 10 decimal places.
So generally, the placeholder for a double type can be %lf.
More content can be found at: Difference between float and double types
tuingke 8 years ago (2018-07-14)
#0 beginner
bry***qiqi@gmail.com
A pointer to the first element of an array is equivalent to a pointer to the array:
#include <stdio.h>
int main ()
{
/* An integer array with 5 elements */
double balance = {1000.0, 2.0, 3.4, 17.0, 50.0};
double *p;
int i;
p = balance;
/* Output each element's value */
printf( "Array values using pointern");
printf( "Array values using p as addressn");
for ( i = 0; i < 5; i++ )
{
printf("p[%d]: %fn", i, p );
}
return 0;
}beginner 6 years ago (2020-09-08)
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