Skill Area 311 Part A

Lecture Overview Binary Numbers Binary Arithmetic ASCII Code Machine Code Instruction Format Advantages and disadvantages of machine code

BINARY NUMBERS

What is “Binary”? A coding system using binary digits 0 and 1 Represent a letter, digit or other character in a computer or other electronic devices 0 1 OFFON

You Do The Math When we talk numbers, we use a base-10 system, because we use ten characters to write out all of our numbers. Computers using binary language operate on a base-2 number system, because the two numbers they use are “0” and “1” Each is a binary digit or “bit” Each bit represents a power of two (2 2, 2 3, 2 4,etc)

Alphabet Our class uses the English language consisting of 26 characters, arranged together in a variety of ways, to communicate. Computers use binary language consisting of 2 characters, arranged together in groups of eight, to communicate. Aa Bb Cc Dd Ee Ff Gg Hh Ii Jj Kk Ll Mm Nn Oo Pp Qq Rr Ss Tt Uu Vv Ww Xx Yy Zz Aa = Zz = bits = 1 byte

The Byte Scale

Binary Arithmetic Binary to Decimal(denary): Binary10110 Power of Two Binary x Power of Two Result = 22

Binary Arithmetic Decimal (denary) to Binary: NumberDivide ByResultRemainder Read from bottom to topResult =10111

Binary Arithmetic Decimal Addition Binary Addition plus 0 produces 0 0 plus 1 produces 1 1 plus 1 produces 0 with a ‘carry’ of 1 into the next most significant place 1 plus 1 plus 1 produces 1 with a ‘carry’ of 1 into the next most significant place 0 plus 0 produces 0 0 plus 1 produces 1 1 plus 1 produces 0 with a ‘carry’ of 1 into the next most significant place 1 plus 1 plus 1 produces 1 with a ‘carry’ of 1 into the next most significant place

Binary Arithmetic Decimal Multiplication Binary Multiplication 5 × ×

Alphanumeric Codes Beside Numbers, we have to represent other types of information: –Letter of alphabet, mathematical symbols American Standard Code for Information Interchange (ASCII)

ASCII Code Uses 7 bits to encode 128 characters 7 bits of ASCII Code –(b 6 b 5 b 4 b 3 b 2 b 1 b 0 ) 2 One ASCII character is stored using a byte One unused bit can be used for other purposes such as representing Greek alphabet, italic type font, etc. The eighth bit can be used for error-detection

ASCII Code 128 different characters – = 62 (letters and decimal digits) –32 special printable characters %, *, $ –34 special control characters (non-printable): BS, CR, etc. Example: –A  65 = ( ), …, a  97 = ( ) –0  48 = ( ), …, 9  57 = ( )

ASCII Code

ASCII Code - Extended

MACHINE CODE OR MACHINE LANGUAGE

What is a “Machine Code”? The lowest and most elementary level of Programming Language. 1 st type of PL to be developed. Represented inside the computer by a String of binary digits (bits) 0 and 1. The symbol 0 stands for the absence of Electric Pulse and 1 for the presence of an electric pulse.

Why “Machine Code”? Their order tells the computer what to do. All other kinds of software need to be translated into machine code before they can be used.

Instruction Format Each instruction is a number that combines: –An operation code (opcode) that picks a hardware function –One or two input operands (where input comes from) –One output operand (where result goes)

Opcode and operand An opcode identifies which basic computer operation in the instruction set is to be performed. It tells the computer to do something. Operands are typically memory or registry addresses. Opcode is like a verb in a sentence, operands are like the subject in a sentence.

Machine Code Instruction LD, A, number Load A with number. A stands for “accumulator” and LD is short for “load” Opcodes and operands are separated by commas

Advantages of Machine Code Makes fast and efficient use of the computer Requires no translator to translate the code i.e. directly understood by the computer

Disadvantages of Machine Code All operations codes have to be remembered All memory addresses have to be remembered It is hard to amend or find errors in a program written in the machine language These languages are machine dependent

Summary Binary Numbers: –Binary digits 0 and 1 –8 bits = 1 byte ASCII: –7 bits –128 characters, 255 with extended Machine Code Opcode and operand