MIDTERM: COSC2425

3 primary I/O levels

1) high-level language functions: contains functions to perform I/O. These functions are portable because they work on a variety of different computer systems and are not dependent on any one operating system. 2)Operating system(OS): Programmers can call operating system functions from a library known as the API(application programming interface). The operating system provides high-level operations such as writing strings to files, reading strings from the keyboard, and allocations blocks of memory. 3)BIOS: a collection of low-level subroutines that communicate directly with hardware devices. Tailored to fit the computer's hardware. Operating systems typically communicate with the BIOS.

word

16 bits

doubleword

32 bits

double quadword

64 bits

byte

8 bits

Assembler

A program that converts source-code programs from assembly language into machine language. Produces both object and listing files.

Input/Output (I/O)

Application programs routinely read input from keyboard and disk files and write output to the screen and to files. I/O need not be accomplished by directly accessing hardware-instead you, can call functions provided by the OS. I/O is available at different access levels, similar to the virtual machine concept.

notional tools

Binary(base2) and hexadecimal(base16) base number systems

stack pointer registers

ESP, & EBP

CPU Status Flags

Sign(when arithmetic generates a negative), Overflow(when arithmetic generates a # too large or too small to fit [-128,127]), Carry(when too large [n>127]), Zero(when 0), Auxiliary(when arithmetic causes a carry from bit 3 to bit 4 in an 8-bit operand), Parity(when LSB is even)

Assembly language

The first language. Has a one-to-one relationship with machine language (one ASM instruction converts to one machine language instruction). Also, it is not portable because it is tied to a specific processor family.

4-basic parts of assembly language

[LABEL] Operands Instruction Mnemonic ;Comments

MOV

a data transfer instruction, copies a source operand to a destination operand. -MOVZX: zero-extends a smaller operand into a larger one. -MOVSX: sign-extends a smaller operand into a larger one.

Registers

a limited number of storage locations that are within a CPU. These can be accessed much more quicker than conventional memory.

debugger

a way to trace the execution of a program and examine the contents of memory at runtime.

INC instruction

adds 1 to an operand

Direct-Offset Operand

adds a displacement to the name of a variable, generating a new offset. This new offset can be used to access data in memory.

ADD instruction

adds a source operand to a destination operand

Logical Segments

are contained in the programs that are named code, data, and stack. Code contains executable instructions. Stack segment holds procedures parameters, local variables, and return addresses. Data holds variables.

General-purpose registers

are primarily used for arithmetic, data movement, and logical operations.

Segment registers

are used as base locations for preassigned memory areas called segments.

Operands

are values passed to instructions. Assembly language instruction can between zero and three operands, each of which can be a register, memory operand, integer expresion, or I/O port number.

Reserved words

are words with special meanings and uses in assembly language that may only be used in the correct context. This is pretty much what syntax means.

Symbolic Constant

associates an identifier with an integer or text expression. 3 directives create symbolic constants: 1)the equal-sign directive(=) associates a symbol name with a constant integer expression. 2)The EQU and TEXTEQU directives associate a symbolic name with a constant integer expression or some arbitrary text.

little-endian order

basically means low-to-high. x86 processors store and retrieve data from memory using this order. The LSB is stored at the first memory address allocated for the data. The remaining bytes are stored in the next consecutive memory positions.

EPROM

can be erased slowly with ultraviolet light and reprogrammed.

Indexed operand

combines a constant with an indirect operand. The constant and register value are added, and the resulting offset is dereferenced.

Linker

combines individual files created by an assembler into a single executable program.

2 basic modes of operation

compatibility and 64-bit mode

flags register

consists of individual binary bits that control the operation of the CPU and reflect the outcome of ALU operations.

Listing file

contains a copy of the program's source code, suitable for printing, with line #s, offset addresses, translated machine language, and a symbol table.

Source file

contains assembly language statements. It is created by a text-editor.

instruction pointer register

contains the address of the next instruction to be executed.

TYPEDEF operator

creates a user-defined type

QWORD/TBYTE

define 8-byte and 10-byte variables, respectively

WORD/SWORD

defines 16-bit variables

DWORD/SDWORD

defines 32 bit-variables

REAL4/REAL8/REAL10

defines 4-byte, 8-byte, and 10-byte real number variables respectively.

BYTE/SBYTE

defines 8-bit variables

XCHG

exchanges the contents of two operands. At least one must be a register.

3 Primary operations

fetch, decode, and execute

VRAM

holds video data. Dual ported, allowing one port to continuously refresh the display while another port writes data to the display.

END

indicates the end point of the execution process to the assembler.

BIOS(basic I/O system)

is a collection of functions that communicate directly with hardware devices.

Directive

is a command embedded in the source code and interpreted by the assembler.

Virtual Machine

is a concept that is an effective way of showing how each layer in a computer architecture represents an abstraction of a machine. Layers can be constructed of hardware or software, and programs written at any layer can related to real-world computer layers, including digital logic, instruction set architecture, assembly language, and high-level languages.

ENDP

is a directive that ends a procedure

Constant Integer Expression

is a mathematical expression involving integer literals, symbolic constants, and arithmetic operators.

Identifier

is a programmer-chosen name identifying a variable, a symbolic constant, a procedure, or a code label. THEY CAN NOT BE RESERVED WORDS.

Indirect Operand

is a register containing the address of data. By surrounding the register with brackets, a program dereferences the address and retrieves the memory data.

String literal

is a sequence of characters enclosed in quotes, optionally ending with a null byte.

Bus

is a series of parallel wires that transmit data among various parts of the computer.

Instruction Mnemonic

is a short keyword that identifies the operation carried out by an instruction.

Character literal

is a single character enclosed in quotes. The assembler converts a character to a byte containing the character's binary ASCII code.

Instruction

is a source code statement that is executed by the processor at runtime.

virtual-8086

is a special case of protected mode.

Label

is an identifier that acts a place marker for instructions or data.

CMOS RAM

is on the system motherboard and stores system setup info. It is refreshed by a battery, so its contents are retained when the computer's power is off.

Direct Operand

is the name of a variable, and represents the variable's address.

LOOP instruction

is used in counting-type loops. It uses ECX as its loop counter in 32bit, and RCX in 64bit.

Central Processor Unit(CPU)

is where calculations and logic processing occur. This is pretty much the most important thing ever created.

Memory Storage unit

is where instructions and data are held while a computer program is running.

DRAM

known as main memory, is where programs and data are kept when a program is running. Inexpensive but must be refreshed every millisecond to avoid losing contents.

PTR operator

overrides a variable's declared size.

ROM

permanently burned into a chip and cannot be erased.

Peripheral Component Interconnect(PCI) bus

provides a convenient upgrade path for Pentium processors.

Precedence

refers to the implied order of operations when an expression contains two or more operators.

SIZEOF operator

returns the # bytes used by an array initializer

LENGTHOF operator

returns the # of elements in an array

OFFSET operator

returns the distance(in bytes) of a variable from the beginning of its enclosing segment.

TYPE operator

returns the size(in bytes) of single variable or of a single element in an array

NEG instruction

reverses the sign of an operand

PROTO

set the function to a prototype

Data Definition Statement

sets aside storage in memory for a variable, and may optionally assign it a name. If multiple intializers are used in the same data definition, its label refers only to the offset of the first initializer.

DEC instruction

subtracts 1 from an operand

SUB instruction

subtracts a source operand from a destination operand

Calling Convention

tells us how to manage a runtime-stack when procedures are called(i.e stdcall), and it's used within the .model directive.

Instruction Execution cycle(IEC)

the execution of a single machine instruction can be divided into a sequence of individual operations is called IEC. Each step within this cycle takes at least one tick of the system clock, which is called the clock cycle.

motherboard

the heart of the computer, which holds the brain(CPU), supports the processors, main memory, I/O connectors, power supply connectors, and expansion slots. Most boards contain an integrated set of several microprocessors and controllers called a chipset. This chipset largely determines the capabilities of the computer.

Floating-point Unit

the x86 has a FPU expressly used for the execution of high-speed floating-point instructions.

Load and execute

this sequence describes how a program is located by the operation system. (loaded into memory and executed by the operating system)

JMP instruction

unconditionally branches to another location

SRAM

used primarily for expensive, high speed cache memory. Doesn't have to be refreshed. CPU cache memory is comprised of SRAM.