【正文】 Assembly Fundamentals Computer Organization and Assembly Languages YungYu Chuang 2020/10/13 with slides by Kip Irvine Announcements ? Homework1 assigned, due on 10/27 ? Next week’s class (10/20) will be taught by TAs ? Midterm examination will be held on the week of 11/10 Chapter Overview ? Basic Elements of Assembly Language ? Example: Adding and Subtracting Integers ? Assembling, Linking, and Running Programs ? Defining Data ? Symbolic Constants Basic elements of assembly language ? Integer constants ? Integer expressions ? Character and string constants ? Reserved words and identifiers ? Directives and instructions ? Labels ? Mnemonics and Operands ? Comments ? Examples Integer constants ? [{+|}] digits [radix] ? Optional leading + or – sign ? binary, decimal, hexadecimal, or octal digits ? Common radix characters: – h – hexadecimal – d – decimal (default) – b – binary – r – encoded real – o – octal Examples: 30d, 6Ah, 42, 42o, 1101b Hexadecimal beginning with letter: 0A5h Integer expressions ? Operators and precedence levels: ? Examples: Real number constants (encoded reals) ? Fixed point . floating point ? Example 3F800000r=+,=42170000r ? double S E M 1 8 23 S E M 1 11 52 177。2 (E127) Real number constants (decimal reals) ? [sign]integer.[integer][exponent] sign → {+|} exponent → E[{+|}]integer ? Examples: 2. + +05 Character and string constants ? Enclose character in single or double quotes – 39。A39。, x – ASCII character = 1 byte ? Enclose strings in single or double quotes – ABC – 39。xyz39。 – Each character occupies a single byte ? Embedded quotes: – ?Say Goodnight, Gracie? – This isn39。t a test Reserved words and identifiers ? Reserved words (Appendix D) cannot be used as identifiers – Instruction mnemonics, directives, type attributes, operators, predefined symbols ? Identifiers – 1247 characters, including digits – case insensitive (by default) – first character must be a letter, _, @, or $ – examples: var1 Count $first _main MAX open_file @@myfile xVal _12345 Directives ? Commands that are recognized and acted upon by the assembler – Part of assembler’s syntax but not part of the Intel instruction set – Used to declare code, data areas, select memory model, declare procedures, etc. – case insensitive ? Different assemblers have different directives – NASM != MASM, for example ? Examples: .data .code PROC Instructions ? Assembled into machine code by assembler ? Executed at runtime by the CPU ? Member of the Intel IA32 instruction set ? Four parts – Label (optional) – Mnemonic (required) – Operand (usually required) – Comment (optional) Label: Mnemonic Operand(s) 。Comment