Computer Networking: A Top-Down Approach (7th Edition)
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Consider the following array declaration, written for a 16 bit processor
How much memory (in bytes) does the whole array require?
![This image contains a snippet of C code typically used in embedded systems programming. Below is a detailed transcription and an explanation.
---
### Code Transcription:
```c
void main(void) {
int idx = 0;
int sample_data[512];
while(1) {
sample_data[idx++] = P3IN & 0x0F;
// . . .
}
}
```
### Explanation:
- **void main(void)**: This is the entry point of the C program. The `void` keyword indicates that the function does not take any arguments.
- **int idx = 0;**: This line declares and initializes an integer variable `idx` to 0. The `idx` variable is typically used as an index for an array.
- **int sample_data[512];**: Here, an array named `sample_data` of size 512 is declared. This array will hold integer values.
- **while(1)**: This starts an infinite loop. The loop will continue to execute indefinitely until the program is terminated or a break statement is encountered.
- **sample_data[idx++] = P3IN & 0x0F;**: Within the loop, data is continuously read from `P3IN`, masked with `0x0F` (to get the lower 4 bits), and stored in the `sample_data` array at the current position indicated by `idx`. After the assignment, `idx` is incremented by one (due to the post-increment operator `++`), preparing the index for the next iteration.
- **// . . .**: This comment represents that additional code could be placed here.
This loop is designed for continuous sampling of data from `P3IN` and storing it in an array, commonly seen in data acquisition applications on embedded systems. The specific masking with `0x0F` indicates only the least significant 4 bits are being stored.](https://content.bartleby.com/qna-images/question/8cc8c426-b479-4d0a-8eda-aecb8e16874c/67242843-6714-47fe-9c83-6d1253d96f7f/5ly7spc_processed.png)
Transcribed Image Text:This image contains a snippet of C code typically used in embedded systems programming. Below is a detailed transcription and an explanation.
---
### Code Transcription:
```c
void main(void) {
int idx = 0;
int sample_data[512];
while(1) {
sample_data[idx++] = P3IN & 0x0F;
// . . .
}
}
```
### Explanation:
- **void main(void)**: This is the entry point of the C program. The `void` keyword indicates that the function does not take any arguments.
- **int idx = 0;**: This line declares and initializes an integer variable `idx` to 0. The `idx` variable is typically used as an index for an array.
- **int sample_data[512];**: Here, an array named `sample_data` of size 512 is declared. This array will hold integer values.
- **while(1)**: This starts an infinite loop. The loop will continue to execute indefinitely until the program is terminated or a break statement is encountered.
- **sample_data[idx++] = P3IN & 0x0F;**: Within the loop, data is continuously read from `P3IN`, masked with `0x0F` (to get the lower 4 bits), and stored in the `sample_data` array at the current position indicated by `idx`. After the assignment, `idx` is incremented by one (due to the post-increment operator `++`), preparing the index for the next iteration.
- **// . . .**: This comment represents that additional code could be placed here.
This loop is designed for continuous sampling of data from `P3IN` and storing it in an array, commonly seen in data acquisition applications on embedded systems. The specific masking with `0x0F` indicates only the least significant 4 bits are being stored.
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