Added example programs

examples/add.in

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+#
+# About
+#
+# This program adds two numbers.
+#
+#
+# Usage
+#
+# $ compiler ./add.in ; ./simple-vm ./add.raw
+#
+#
+#
+
+ store #1, 10
+ store #2, 20
+ add #0, #1, #2
+ print_int #0
+
+ # add newline to the output
+ store #1, "\n"
+ print_str #1

examples/call.in

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+#
+# About
+#
+# This program demonstrates that we can use subroutines.
+#
+#
+# Usage
+#
+# $ compiler ./call.in ; ./simple-vm ./call.raw
+#
+#
+#
+ store #1, 15
+ call print
+
+ store #1, 240
+ call print
+
+ store #1, 255
+ call print
+
+ exit
+
+
+#
+# This routine will print the integer stored in register #1
+#
+# Then it will print a newline.
+#
+# Then it will return to the caller.
+#
+:print
+ print_int #1
+ store #1, "\n"
+ print_str #1
+ ret

examples/compare.in

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+#
+# About
+#
+# This program compares the number in a register with a constant.
+#
+#
+# Usage
+#
+# $ compiler ./compare.in ; ./simple-vm ./compare.raw
+#
+#
+#
+
+ store #1, 44
+ cmp #1, 44
+ jmpz equal
+
+ store #1, "Inequal\n"
+ print_str #1
+ exit
+
+:equal
+ store #1, "EQUAL\n"
+ print_str #1
+
+
+ store #1, "Steve"
+ cmp #1, "Kemp"
+ jmpnz str1
+
+ store #1, "Eek string 1 compare failed - BUG?\n"
+ print_str #1
+ exit
+
+:str1
+ store #1, "Steve"
+ cmp #1, "Steve"
+ jmpz str2
+
+ store #1, "Eek string 2 compare failed - BUG?\n"
+ print_str #1
+ exit
+
+
+:str2
+ store #1, "String comparisions OK\n"
+ print_str #1
+ exit

examples/concat.in

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+#
+# About
+#
+# Use a conditional jump to loop ten times, building up a string as we go.
+#
+#
+# Usage
+#
+# $ compiler ./concat.in ; ./simple-vm ./concat.raw
+#
+#
+#
+
+ store #1, "Counting bananas"
+ print_str #1
+
+ store #1, 10
+ store #2, 1
+
+ store #3, ""
+ store #4, " banana"
+:repeat
+
+ #
+ # This means "reg1 = reg1 - reg2"
+ #
+ sub #1, #1, #2
+
+ concat #3, #3, #4
+ print_str #3
+
+ # add newline to the output
+ store #5, "\n"
+ print_str #5
+
+ #
+ # This jump only occur if the zero-flag is set.
+ #
+ jmpnz repeat
+
+
+ store #1, "Done"
+ print_str #1
+
+ exit

examples/dec.in

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+#
+# About
+#
+# This program decrements an integer.
+#
+#
+# Usage
+#
+# $ compiler ./dec.in ; ./simple-vm ./dec.raw
+#
+#
+#
+
+ store #1, 3
+ store #0, "Stored in register #1 -> 3\n"
+ print_str #0
+
+
+ dec #1
+ store #0, "Decremented contents of register #1 -> 2\n"
+ print_str #0
+ jmpz empty
+
+ dec #1
+ store #0, "Decremented contents of register #1 -> 1\n"
+ print_str #0
+ jmpz empty
+
+ dec #1
+ store #0, "Decremented contents of register #1 -> 0\n"
+ print_str #0
+ jmpz empty
+
+ dec #1
+ store #0, "Decremented contents of register #1 -> -1 [not reached]\n"
+ print_str #0
+ jmpz empty
+
+:empty
+ exit

examples/equal.in

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+#
+# About
+#
+# This program tests our comparision operation.
+#
+#
+# Usage
+#
+# $ compiler ./equal.in ; ./simple-vm ./equal.raw
+#
+#
+#
+
+ store #1, 20
+ store #2, 30
+
+ cmp #1, #2
+ jmpz twenty_eq_thirty
+
+ store #2, 20
+ cmp #1, #2
+ jmpz twenty_eq_twenty
+
+ exit
+
+:twenty_eq_twenty
+ store #0, "20 == 20 - OK!\n"
+ print_str #0
+ exit
+
+:twenty_eq_thirty
+ store #0, "20 == 30 - Bug!\n"
+ print_str #0
+ exit

examples/hello.in

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+
+ store #1, "Hello, World!\n"
+ print_str #1
+ exit

examples/jump.in

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+#
+# About
+#
+# This program only outputs some static strings and an integer
+#
+# However it does prove that the goto/label handling is correct.
+#
+#
+# Usage
+#
+# $ compiler ./jump.in ; ./simple-vm ./jump.raw
+#
+#
+#
+
+ store #1, "Steve Kemp\n"
+ print_str #1
+ goto number
+
+ # padding here - just for amusement.
+ nop
+ exit
+
+:kirsi
+ store #1, "Kirsi Kemp\n"
+ print_str #1
+ exit
+
+:number
+ store #1, 32
+ print_int #1
+
+ # add newline to the output
+ store #1, "\n"
+ print_str #1
+
+ goto kirsi
+

examples/loop.in

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+#
+# About
+#
+# Use a conditional jump to loop ten times, the conditional will trigger
+# if a "SUB" operation results in <0.
+#
+#
+# Usage
+#
+# $ compiler ./loop.in ; ./simple-vm ./loop.raw
+#
+#
+#
+
+ store #1, "Counting from ten to zero\n"
+ print_str #1
+
+ store #1, 11
+ store #2, 1
+:repeat
+
+ #
+ # This means "reg1 = reg1 - reg2"
+ #
+ sub #1, #1, #2
+ print_int #1
+
+ # add newline to the output
+ store #5, "\n"
+ print_str #5
+
+ #
+ # This jump only occur if the zero-flag is set.
+ #
+ jmpnz repeat
+
+
+ store #1, "Done\n"
+ print_str #1
+
+ exit

examples/memcpy.in

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+#
+# About
+#
+# This program copies a bunch of memory about, then jumps to it.
+#
+#
+# Usage
+#
+# $ compiler ./memcpy.in ; ./simple-vm ./memcpy.raw
+#
+#
+#
+
+ goto run
+ :code
+
+ #
+ # This is the code we're going to copy and execute.
+ #
+ store #1, "Steve Kemp\n"
+ print_str #1
+ store #1, "memcpy works\n"
+ print_str #1
+ exit
+ :code_end
+
+ :run
+ #
+ # Copy the memory between `code` and `code_end` to 0x5000.
+ #
+
+ # First of all calcuate the length
+ store #2, code
+ store #3, code_end
+ sub #3, #3, #2
+
+ # Show the length of the code we're copying
+ # Remember the result is in #3.
+ store #1, "Code length is "
+ print_str #1
+ print_int #3
+ store #1, "\n"
+ print_str #1
+
+ # setup the copy and run it
+ store #1, 0x5000
+ store #2, code
+ memcpy #1, #2, #3
+
+ # Jump to the copied code.
+ goto 0x5000