BME303_lecture11 - 1 BME303 Intro to Computing 1...

Unformatted text preview: 1 BME303 Intro. to Computing 1 Programming Languages • Generally, programming languages describe programs at various levels of detail, where the coarsest classification distinguishes – high level languages (e.g., C, C++, Fortran, Pascal, etc.) – low level languages which are much “closer” to the underlying ISA • Whatever the level, a program written in that language must be translated to a program in machine language (ML) , i.e., its instructions are in the computer’s ISA. Problem Language Machine (ISA) Architecture Algorithms Micro-architecture Circuits Devices Human Analytical thinker Programmer Compiler, Assembler Electrons BME303 Intro. to Computing 2 Chapter 7: Assembly Language High-level Language Program Assembly Language Program Machine Language Program Compiler Assembler Programmer Programmer Computer Computer Computer • Instead of writing in machine code we can write our programs using a more "friendly“ programming language: – Assembly language (now) – C++, MATLAB, LabVIEW (later) • System software provides us with software tools to translate programs into machine code: – Assembler – Compiler 2 BME303 Intro. to Computing 3 Chapter 7: Assembly Language High-level Language Program Assembly Language Program Machine Language Program Compiler Assembler Programmer Programmer Computer Computer Computer • Outline: – Assembly Language (Instructions…) – Assembly process – Style BME303 Intro. to Computing 4 The Instruction Mnemonics • Mnemonic: A system to develop or improve the memory. • Better term: Symbolic Name • ADD, AND, NOT, LD, LDI, LDR, LEA , ST, STI, STR, BR, TRAP, JMP, JSR/JSSR, RTI • Still have a one-to-one correspondence with Machine Language Instructions 3 BME303 Intro. to Computing 5 We’ve seen mnemonics already: Address Instruction Comments x30F6 1110 001 111111101 LEA R1 #-3 PC +1 = x30F7 R1 PC +1 − 3 = x30F4 x30F7 0001 010 001 1 01110 ADD R2 R1 #14 R2 R1 + 14 = x3102 x30F8 0011 010 111111011 ST R2 #-5 PC +1 −5 = x30F9 − 5 = x30F4 M[0x30F4] R2 x30F9 0101 010 010 1 00000 AND R2 R2 #0 R2 AND x0000 = x0000 R2 0 x30FA 0001 010 010 1 00101 ADD R2 R2 #5 R2 R2 + 5 = 5 BME303 Intro. to Computing 6 Instruction Format • In the LC-3 assembly language, instead of instructions being 16-bit words, they have the following format: LABEL OPCODE OPERANDS ;COMMENTS • The OPCODE and OPERAND parts are mandatory ; the LABEL and COMMENTS parts are optional • OPCODE is a symbolic name for the 4-bit opcode of the corresponding LC-3 machine language (ML) instruction • OPERANDS are likewise symbolic names 4 BME303 Intro. to Computing 7 Labels and Comments • Labels are symbolic names that identify memory locations referred to explicitly in the Assembly Language Program (APL), e.g., the location contains – the target of a branch instruction – a value that is loaded or stored • The optional comments part of the instruction (begins with a leading semi-colon) consists of...
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