```
12 23 34 45 56
34 23 56 21 43
12 57 98 34 12

```

The above is the content of a txt file.

With C, i can use `fgetc(myFile)` to get the first integer and store into an integer variable.

I will check whether it is 12. 

if it is 12, i want to replace with 25. How do i exactly replace it a certain number.

How do i rewrite a certain part of it?

Or do i store every number into an array, replace all 12s with another numbers and overwrite the whole file??