# File Handling

> Cambridge Assessment International Education (CAIE) Pseudocode Reference Guide
> Applicable Syllabus: **IGCSE & A Level**

Cambridge IGCSE and AS & A Level sequential text files (OPENFILE, READFILE, WRITEFILE, EOF), with 9618 random-access extensions.

---

Files must be opened before use with `OPENFILE` and closed with `CLOSEFILE`. Sequential text files are covered by IGCSE and AS & A Level. Random-access records are an AS & A Level extension.

### 9.1 Text Files

| Command | Description |
|---------|-------------|
| `OPENFILE <file> FOR READ` | Open for reading lines sequentially |
| `OPENFILE <file> FOR WRITE` | Create or truncate file for writing |
| `OPENFILE <file> FOR APPEND` | Open to append data after existing contents |
| `READFILE <file>, <var>` | Read next line into a STRING variable |
| `WRITEFILE <file>, <data>` | Write data as a new line to the file |
| `EOF(<file>)` | Returns TRUE if no more lines remain to be read |
| `CLOSEFILE <file>` | Close and flush the file |

### Text File Example — Copy with Replacement

```pseudocode
// runnable
// Text file copy demo
// Create sample input in the sandbox virtual filesystem
OPENFILE "FileA.txt" FOR WRITE
WRITEFILE "FileA.txt", "First line"
WRITEFILE "FileA.txt", ""
CLOSEFILE "FileA.txt"
DECLARE LineOfText : STRING
OPENFILE "FileA.txt" FOR READ
OPENFILE "FileB.txt" FOR WRITE
WHILE NOT EOF("FileA.txt")
   READFILE "FileA.txt", LineOfText
   IF LineOfText = "" THEN
      WRITEFILE "FileB.txt", "----------------------------"
   ELSE
      WRITEFILE "FileB.txt", LineOfText
   ENDIF
ENDWHILE
CLOSEFILE "FileA.txt"
CLOSEFILE "FileB.txt"
```

### 9.2 Random Files (9618)

| Command | Description |
|---------|-------------|
| `OPENFILE <file> FOR RANDOM` | Open for direct record address access |
| `SEEK <file>, <address>` | Move file pointer to target record number |
| `GETRECORD <file>, <var>` | Read record structure at active file pointer |
| `PUTRECORD <file>, <var>` | Write record structure at active file pointer |

### Random File Example

This fragment assumes the record type and an existing data file have already been created.

```pseudocode
DECLARE Pupil : StudentRecord
DECLARE NewPupil : StudentRecord

NewPupil.LastName <- "Johnson"
NewPupil.FirstName <- "Leroy"
NewPupil.YearGroup <- 6

OPENFILE "StudentFile.Dat" FOR RANDOM
FOR Position <- 20 TO 10 STEP -1
   SEEK "StudentFile.Dat", Position
   GETRECORD "StudentFile.Dat", Pupil
   SEEK "StudentFile.Dat", Position + 1
   PUTRECORD "StudentFile.Dat", Pupil
NEXT Position

SEEK "StudentFile.Dat", 10
PUTRECORD "StudentFile.Dat", NewPupil
CLOSEFILE "StudentFile.Dat"
```


---

* Previous Topic: [Procedures & Functions](https://csmasters.dev/docs/pseudocode/subroutines.md)
* Next Topic: [Object-Oriented Programming](https://csmasters.dev/docs/pseudocode/oop.md)