### Part a
Write the contents of the Text Buffer and the Statement Descriptor Table.
**Text Buffer:** This stores the program as a sequence of characters.
```
10 FOR
20 FOR I=1 TO 2
30 FOR J=1 TO 3
40 CALL 100
50 NEXT J
60 NEXT I
70 END
100 A=A+5
110 RETURN
```
**Statement Descriptor Table (SDT):** This table contains metadata about each line in the program, such as the descriptor number, line number, offset in the text buffer, and the next descriptor.
| Descriptor No. | Line No. | Text Buffer Offset | Next Descriptor |
|----------------|----------|--------------------|-----------------|
| 1 | 10 | 0 | 2 |
| 2 | 20 | 8 | 3 |
| 3 | 30 | 23 | 4 |
| 4 | 40 | 37 | 5 |
| 5 | 50 | 48 | 6 |
| 6 | 60 | 56 | 7 |
| 7 | 70 | 64 | 8 |
| 8 | 100 | 70 | 9 |
| 9 | 110 | 79 | - |
### Part b
Number of parse tables generated for each statement.
- **FOR loops (Lines 20, 30):** Each FOR loop will have its own parse table. As the inner loop runs 3 times for each iteration of the outer loop, the parse tables will be generated as follows:
- Line 20 (FOR I=1 TO 2): 1 time
- Line 30 (FOR J=1 TO 3): 2 times for each outer loop iteration (3 times) = 6 times
- **CALL statement (Line 40):** It will be parsed 6 times (once for each iteration of the inner loop).
- **NEXT statements (Lines 50, 60):**
- Line 50: 6 times (matching the inner loop)
- Line 60: 2 times (matching the outer loop)
- **END statement (Line 70):** 1 time
- **A=A+5 statement (Line 100):** 1 time (called by CALL)
- **RETURN statement (Line 110):** 1 time
Total parse tables: \(1 (FOR I) + 6 (FOR J) + 6 (CALL) + 6 (NEXT J) + 2 (NEXT I) + 1 (END) + 1 (A=A+5) + 1 (RETURN) = 24\)
### Part c
Draw the parse table for the statement `100 A=A+5`.
**Parse Table for `A=A+5`**
| Descriptor No. | Line No. | Text Buffer Offset | Next Descriptor |
|----------------|----------|--------------------|-----------------|
| 1 | 100 | 0 | - |
### Part d
Draw the LCTs and show the contents of LRS at each step.
1. **Line Control Tables (LCTs)**: LCTs manage the control flow of lines.
2. **Loop Repetition Stack (LRS)**: Manages the state of nested loops.
**LCT Representation:**
| Iteration | Line No. | I | J |
|-----------|----------|----|---|
| 1 | 20 | 1 | |
| 2 | 30 | 1 | 1 |
| 3 | 40 | 1 | 1 |
| 4 | 50 | 1 | 1 |
| 5 | 30 | 1 | 2 |
| 6 | 40 | 1 | 2 |
| 7 | 50 | 1 | 2 |
| 8 | 30 | 1 | 3 |
| 9 | 40 | 1 | 3 |
| 10 | 50 | 1 | 3 |
| 11 | 60 | 1 | |
| 12 | 20 | 2 | |
| 13 | 30 | 2 | 1 |
| 14 | 40 | 2 | 1 |
| 15 | 50 | 2 | 1 |
| 16 | 30 | 2 | 2 |
| 17 | 40 | 2 | 2 |
| 18 | 50 | 2 | 2 |
| 19 | 30 | 2 | 3 |
| 20 | 40 | 2 | 3 |
| 21 | 50 | 2 | 3 |
| 22 | 60 | 2 | |
| 23 | 70 | | |
**LRS Content at each step:**
| Step | I | J |
|------|---|---|
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 1 | 3 |
| 4 | 2 | 1 |
| 5 | 2 | 2 |
| 6 | 2 | 3 |
Explanation:
- The outer loop runs twice, with `I` values 1 and 2.
- For each `I`, the inner loop runs three times, with `J` values 1, 2, and 3.
- The CALL statement (line 40) invokes the A=A+5 operation each time it is encountered in the loop.
