Update README with an example

README.md

@@ -7,15 +7,124 @@ This is a toy project where I've created an emulator, assembler and a dissasembl
 The emulator takes either assembly code that the assembler transforms to machine code or native machine code directly which then the emulator executes.
 
 
+## Example program
+
+The assembler supports the syntax found at Nick Morgan's [Easy6502](https://skilldrick.github.io/easy6502/) which looks something like this:
+
+
+```asm
+define counter $00  ; Address of counter
+define max 10       ; Num of times to loop
+
+main:
+  jsr init          ; Initialize counter
+  jsr loop          ; Run loop
+  jmp exit          ; Exit program
+
+init:
+  lda #0            ; Load 0 into accumulator
+  sta counter       ; Store accumulator into counter address
+  rts
+
+loop:
+  lda counter       ; Load what's in counter address into accumulator
+  cmp #max          ; Compare accumulator to max value
+  beq done          ; If equal, branch to done
+  inc counter       ; Increment counter
+  jmp loop          ; Jump to loop
+done:
+  rts               ; Return back to main
+
+exit:
+```
+
+
+#### Supported syntax
+
+- Values (8 bit bytes and 16 bit words)
+    - Hex: `$ff`
+    - Binary: `%1101`
+    - Decimal `42`
+- Labels: `main:`
+- Constants: `define max $ff`
+
+
+### Assembling
+
+```bash
+$ cargo run -r --bin asm -- examples/loop.asm
+   Compiling mos6502 v0.1.0 (/home/david/Dev/mos6502)
+    Finished release [optimized] target(s) in 0.37s
+     Running `target/release/asm examples/loop.asm`
+
+8000: 20 09 08 20 0e 08 4c 1a 08 a9 00 85 00 60 a5 00
+8010: c9 0a f0 05 e6 00 4c 0e 08 60
+```
+
+
+### Disassembling
+
+
+```bash
+$ cargo run -r --bin dism -- a.bin
+    Finished release [optimized] target(s) in 0.01s
+     Running `target/release/dism a.bin`
+ Addr  Hexdump   Instructions
+-----------------------------
+$8000  20 09 08  JSR $0809
+$8003  20 0E 08  JSR $080E
+$8006  4C 1A 08  JMP $081A
+$8009  A9 00     LDA #$00
+$800B  85 00     STA $00
+$800D  60        RTS
+$800E  A5 00     LDA $00
+$8010  C9 0A     CMP #$0A
+$8012  F0 05     BEQ $05
+$8014  E6 00     INC $00
+$8016  4C 0E 08  JMP $080E
+$8019  60        RTS
+```
+
+
+### Emulating
+
+Running this program with a modified emulator that in the end prints the contents of the memory
+at address `0x0000` (Zero page address `0x00`):
+
+```bash
+~/Dev/mos6502(master ✗) cargo run -r --bin emu -- a.bin
+    Finished release [optimized] target(s) in 0.01s
+     Running `target/release/emu a.bin`
+Memory address 0x0000: 0x0a
+```
+
+Here we see `0x0a`, which in decimal is `10` just we intended!
+
+
+## Future development
+
+- dot directives
+    - `.org $8000`
+    - `.byte 42`
+    - `.word $8000`
+- `#"A"`
+- Graphical state for the emulator
+- Peripherals - I/O would be fun to have...
+
+
 ## References
 
-https://skilldrick.github.io/easy6502/
-http://www.6502.org/tutorials/6502opcodes.html
-https://en.wikibooks.org/wiki/6502_Assembly#Load_and_Store
-https://www.masswerk.at/6502/6502_instruction_set.html#LDA
-https://www.nesdev.org/wiki/Nesdev#6502
-https://www.nesdev.org/6502.txt
-https://www.nesdev.org/wiki/6502_cycle_times
-https://github.com/mre/mos6502/tree/master
-https://en.wikipedia.org/wiki/Interrupts_in_65xx_processors
-http://6502.org/tutorials/interrupts.html
+I've found many great resources and project which helped this project.
+
+- https://skilldrick.github.io/easy6502/
+- http://www.6502.org/tutorials/6502opcodes.html
+- https://en.wikibooks.org/wiki/6502_Assembly#Load_and_Store
+- https://www.masswerk.at/6502/6502_instruction_set.html#LDA
+- https://www.nesdev.org/wiki/Nesdev#6502
+- https://www.nesdev.org/6502.txt
+- https://www.nesdev.org/wiki/6502_cycle_times
+- https://github.com/mre/mos6502
+- https://en.wikipedia.org/wiki/Interrupts_in_65xx_processors
+- http://6502.org/tutorials/interrupts.html
+- [Ben Eater's videos](https://www.youtube.com/playlist?list=PLowKtXNTBypFbtuVMUVXNR0z1mu7dp7eH)
+- [Javidx9's videos](https://www.youtube.com/playlist?list=PLrOv9FMX8xJHqMvSGB_9G9nZZ_4IgteYf)