This code is written in the assembly language for the...

June 30, 2025 at 11:44 PM

// ===== Draw 'C' =====
@252
D=A
@16384
M=D
@192
D=A
@16385
M=D
@128
D=A
@16386
M=D
@128
D=A
@16387
M=D
@128
D=A
@16388
M=D
@192
D=A
@16389
M=D
@252
D=A
@16390
M=D
@0
D=A
@16391
M=D

// ===== Draw 'S' =====
@252
D=A
@16392
M=D
@192
D=A
@16393
M=D
@128
D=A
@16394
M=D
@124
D=A
@16395
M=D
@6
D=A
@16396
M=D
@6
D=A
@16397
M=D
@252
D=A
@16398
M=D
@0
D=A
@16399
M=D

// ===== Draw '2' =====
@252
D=A
@16400
M=D
@6
D=A
@16401
M=D
@12
D=A
@16402
M=D
@24
D=A
@16403
M=D
@48
D=A
@16404
M=D
@96
D=A
@16405
M=D
@126
D=A
@16406
M=D
@0
D=A
@16407
M=D

// ===== Draw '2' again =====
@252
D=A
@16408
M=D
@6
D=A
@16409
M=D
@12
D=A
@16410
M=D
@24
D=A
@16411
M=D
@48
D=A
@16412
M=D
@96
D=A
@16413
M=D
@126
D=A
@16414
M=D
@0
D=A
@16415
M=D

// ===== Draw '0' =====
@124
D=A
@16416
M=D
@198
D=A
@16417
M=D
@198
D=A
@16418
M=D
@198
D=A
@16419
M=D
@198
D=A
@16420
M=D
@198
D=A
@16421
M=D
@124
D=A
@16422
M=D
@0
D=A
@16423
M=D

// ===== END =====
(END)
@END
0;JMP

This code is written in the assembly language for the Hack computer platform, which is part of the architecture introduced in the book The Elements of Computing Systems by Nisan and Schocken. It leverages memory-mapped graphics to draw characters on the screen. Here's a breakdown of what the code does:

Overview

The code draws several characters ('C', 'S', '2', '2', and '0') on the screen using pixel-based representations stored in the memory-mapped display. It directly sets specific screen memory addresses (@16384 to @16423) to certain values representing pixels that correspond to parts of the characters. After drawing all characters, the program loops indefinitely at the (END) label.

Key Concepts

Memory Mapping to Display: Pixels on the screen are represented by bits of memory starting at address 16384 (i.e., @16384). Each word represents 16 horizontal pixels, and the vertical coordinate corresponds to subsequent memory addresses.
Direct Memory Manipulation: The code sets specific words in the memory to binary values (interpreted as integers in assembly) to "turn on" specific pixels on the screen.

Step-by-Step Details

1. Draw 'C'

This part draws the letter 'C':

It writes values (252, 192, 128, etc.) to consecutive memory addresses starting at @16384. Each of these values represents a row of pixels in the 'C' shape:
- 252: Top of the 'C' (leftmost upper horizontal pixels turned on).
- 192, 128: Middle left pixels forming the vertical line of the 'C'.
- 252: Bottom part of the 'C' (leftmost lower horizontal pixels turned on).

2. Draw 'S'

This part draws the letter 'S':

Similar to 'C', values (@252, 192, 128, etc.) are written to memory addresses starting at @16392. Each value forms part of the 'S' shape:
- 252: Top of the 'S'.
- 124: Middle horizontal bar.
- 6: Vertical right-side section.
- 252: Bottom of the 'S'.

3. Draw '2'

This part draws the digit '2':

Starting at @16400, it uses values (252, 6, 12, etc.) to map a pixel representation of '2':
- 252: Top horizontal bar of the '2'.
- 6: Top-right segment of the '2'.
- 126: Bottom curved shape.

4. Draw '2' Again

The digit '2' is drawn again, starting at @16408. This is a repetition of the previous section for another identical '2'.

5. Draw '0'

This part draws the digit '0':

Starting at @16416, it uses values (124, 198, etc.) to render the circular shape of '0':
- 124: Top horizontal bar.
- 198: Vertical sides.

6. End Program

The (END) label marks the end of the program. Following it is an infinite jump loop:

(END)
@END
0;JMP

After completing all the drawing instructions, the program jumps back to itself endlessly, effectively halting further execution.

Summary

The code draws the characters "CS220" on the screen in a graphical representation by setting specific memory values that correspond to pixel configurations.
It uses the memory-mapped display starting from address 16384 to achieve this.
After drawing, the program enters an infinite loop to terminate execution.

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