9.6. Self-assessment questions

9.6. Self-assessment questions
	Chapter 9. Reading and writing with files

There is something wrong with this piece of code. What it is?:
```
1    FILE *fptr;
2    char b = ‘b’;
3    char *c = &b;
4    if (fptr = fopen(“file.txt”, “r”))!= NULL) 
5    {
6      while(!feof(fptr)) 
7      {
8          fwrite(c, sizeof(char),1,fptr)
9          printf(“Character: %c”,*c);
10     }
11     fclose(fptr);
12   } 
```
- Whatever it happens with the file when is open, it has to be closed; therefore, the function call fclose(fptr) in line 11 must be located outside the if statement, after line 11.
- The first argument in read/write functions (fread/fwrite) is the variable address where the data is going to be read from or write to; therefore, the correct statement in line 8 is fwrite(&c, sizeof(char),1,fptr);
- The function printf needs the address of the char variable, not its value; therefore, the correct sentence in line 9 is printf(“Character: %c”,c);
- The program tries to write in a file that has been opened just to be read.
- Code is correct, there is nothing wrong with it.
You open the file fptr, whose size is 100 bytes. Which of these pairs of sentences is equivalent?
- rewind(fptr);
  fseek(fptr,-0L, SEEK_END);
- rewind(fptr);
  fseek(fptr,100L, SEEK_END);
- rewind(fptr);
  fseek(fptr,0L, SEEK_CUR);
- rewind(fptr);
  fseek(fptr,-100L, SEEK_SET);
- All the previous pairs are equivalent.
- None above.
You open the file fptr. You start reading byte by byte, till the end of file. At that point, which of these sentences is correct?:
- The file position indicator has remained unchanged at the beginning of the file; it can just be moved with functions rewind or fseek.
- The file position indicator is located at the end of the file; it has been moving byte by byte, while reading.
- The file position indicator has remained unchanged at the beginning of the file; it just moves when writing, not when reading.
- None above.

UC3M

Telematic/Audiovisual Syst./Communication Syst. Engineering

Systems Architecture

September 2017 - January 2018

9.6. Self-assessment questions


9.5. Direct file manipulation		9.7. Further reading