cfeck / alek

Assembly Learning Environment for Kids

ALEK

Assembly Learning Environment for Kids

Purpose

Teach kids elementary concepts of memory and CPU, including:

• instruction codes
• character codes
• RGB color codes
• memory addresses
• ALU and registers
• call stack
• memory-mapped output

Quick Start

• install Python 3 and PyQt 5
• run "alek.py" with Python
• click the menu arrow in the upper-right corner
• click menu "Demo 1: Hi"
• click the "Exec" button until the processor is halted
• the video output now displays "Hi"
• click menu "Reset" to enable execution again

Architecture

Memory

• is organized in 10 pages x 10 rows x 10 cells = 1000 cells
• select page with the Memory tabs

Pages

0..4    code or data
5..6    (reserved for shared pages)
7..8    mapped to the video output
9       stack page

Cells

• contain a 3-digit decimal number (0..999, no hex/binary needed)
• each cell has an address, also in range 0..999
• double-click a cell to edit it via keyboard
• click on the Code table entries to enter/edit instructions
• drag-select multiple cells for menu "Clear Memory Cells"

CPU

• 4 general registers R1..R4
• IP register (Instruction Pointer) has the address of the next instruction
• SP register (Stack Pointer) has the address of last pushed number
• ALU can perform arithmetic operations (+ −) and comparison with numbers
• comparison results "less than (<)", "equal to (=)" , or "greater than (>)"
• data flow is not yet visualized during execution

Codes for CPU Instructions

1ds     ADD     add to destination d the source s
2ds     SUB     subtract from destination d the source s
5ds     MOV     move to destination d the source s
6ds     CMP     compare numbers from sources d and s
7cs     JMP     jump if condition c is satisfied to cell s
95d     POP     pop (from stack) to destination d
96s     PUSH    push (to stack) the source s
97s     CALL    push IP and jump to cell s
997     RET     pop to IP (return to caller)
999     HLT     halt the processor

(See the table in the "Code" tab)

Addressing

0       ###         data immediately after the code (only for source)
1..4    R1..R4      data in register
5..8    (R1)..(R4)  data in memory addressed by register
9       (##)        data in memory with absolute address

Condition Codes

1       <
2       >
4       =
add codes for combinations, e.g. ">=" is 6

Code for Characters

5       space
6..9    elementary punctation
10..29  symbols/punctation
30..39  0..9 digits
41..66  A..Z letters
71..96  a..z letters

(See the table in the "Char" tab)