CMSC Machine Architecture and Number Systems Topics Major Computer Components Bits, Bytes, and Words The Decimal Number System The Binary Number System Converting from Binary to Decimal Converting from Decimal to Binary The Hexidecimal Number System

CMSC Major Computer Components Central Processing Unit (CPU) Bus Main Memory (RAM) Secondary Storage Media I / O Devices

CMSC The CPU Central Processing Unit The “brain” of the computer Controls all other computer functions In PCs (personal computers) also called the microprocessor or simply processor.

CMSC The Bus Computer components (Such as: the CPU, Main Memory, & Hard Disks) are connected by a bus. A bus is a group of parallel wires that carry control signals and data between components.

CMSC Main Memory Main memory holds information such as computer programs, numeric data, or a document created by a word processor. Main memory is made up of capacitors. If the capacitor is charged, then its state is said to be 1 or ON. We could also say the bit is set. If the capacitor does not have a charge, then its state is 0 or OFF. We could also say that the bit is reset or cleared. 0,1

CMSC Main Memory (con’t) Memory is divided into cells, where each cell contains 8 bits (1’s or 0’s). Eight bits is called a byte. Each of these cells is numbered. The number associated with a cell is known as its address. Main memory is volatile storage. That is, if power is lost, the information in main memory is lost.

CMSC Main Memory (con’t) In addition to the circuitry that holds the bits, there are other circuits that allow other components (Like the CPU) to: o get the information held at a particular address in memory, known as a READ, o or store information at a particular address in memory, known as a WRITE.

CMSC Main Memory (con’t) All addresses in memory can be accessed in the same amount of time. We do not have to start at address 0 and read everything until we get to the address we really want. We can go directly to the address we want and access the data. That is why we call main memory RAM (Random Access Memory).

CMSC Secondary Storage Media Disks -- floppy, hard, removable (random access) Tapes (sequential access) CDs (random access) DVDs (random access) Secondary storage media store files that contain o computer programs o data files o other types of information This type of storage is called persistent (permanent) storage because it is non-volatile.

CMSC I/O (Input/Output) Devices Information input/output is handled by I/O (peripheral) devices. A peripheral device is a component that is not an integral part of the computer. Examples: o monitor o keyboard o mouse o disk drive (floppy, hard, removable) o CD or DVD drive o printer o scanner

CMSC Computer/Peripheral Communication Ports o locations through which data can enter or leave the computer (plugs on back) o identified by port numbers like memory cells are identified by addresses

CMSC Parallel and Serial Communication l Refer to the manner in which bit patterns are transferred with respect to time. l Parallel - All the bits of a pattern are transferred at the same time, with each bit being transferred on a separate line. Requires multi-wire cables. l Serial - Transmits one bit at a time. Slower, but uses a simpler data path.

CMSC Bits, Bytes, and Words A bit is a single binary digit (a 1 or 0). A byte is 8 bits A word is 32 bits or 4 bytes (machine dependant) Long word = 8 bytes = 64 bits Quad word = 16 bytes = 128 bits Programming languages use these standard number of bits when organizing data storage and access. What do you call 4 bits ?? (hint: it is a small byte)

CMSC From “C How to Program” 4 rd edition Deitel & Deitel, ISBN# = Items covered in the this part of class: Page Number Systems: binary, decimal, hex Page Number System Representations Page Converting Binary to Decimal - Converting Decimal to Binary/Hex

CMSC The Binary Number System The on and off states of the capacitors in RAM can be thought of as the values 1 and 0. Therefore, thinking about how information is stored in RAM requires knowledge of the binary (base 2) number system. Let’s review the decimal (base 10) number system first.

CMSC The Decimal Number System The decimal number system is a positional number system. Example: X X X X 10 3

CMSC The Decimal Number System (con’t) The decimal number system is also known as base 10. The values of the positions are calculated by taking 10 to some power. Why is the base 10 for decimal numbers? o Because we use 10 digits, the digits 0 through 9.

CMSC The Binary Number System The binary number system is called binary because it uses base 2. The values of the positions are calculated by taking 2 to some power. Why is the base 2 for binary numbers ? o Because we use 2 digits, the digits 0 and 1.

CMSC The Binary Number System (con’t) The binary number system is also a positional numbering system. Instead of using ten digits, 0 - 9, the binary system uses only two digits, 0 and 1. Example of a binary number and the values of the positions:

CMSC Converting from Binary to Decimal X 2 0 = X 2 1 = 0 0 X 2 2 = = = 16 0 X 2 3 = = = 32 0 X 2 4 = = = 64 0 X 2 5 = = 81 X 2 6 = 64 65

CMSC Converting from Binary to Decimal (con’t) Practice conversions: Binary Decimal

CMSC Converting Decimal to Binary l First make a list of the values of 2 to the powers of 0 to 8, then use the subtraction method. 2 0 = 1, 2 1 = 2, 2 2 = 4, 2 3 = 8, 2 4 = 16, 2 5 = 32, 2 6 = 64, 2 7 = 128, 2 8 = 256 l Example:

CMSC Counting in Binary l Binary l Decimal equivalent

CMSC Addition of Binary Numbers l Examples:

CMSC Addition of Large Binary Numbers l Example showing larger numbers:

CMSC Working with Large Numbers = ? Humans can’t work well with binary numbers; there are too many digits to deal with. Memory addresses and other data can be quite large. Therefore, we sometimes use the hexadecimal number system.

CMSC Hexadecimal Binary Hex Written:

CMSC What is Hexadecimal really ? Binary Hex A number expressed in base 16. It’s easy to convert binary to hex and hex to binary because 16 is 2 4.

CMSC Hexadecimal l Binary is base 2, because we use two digits, 0 and 1 l Decimal is base 10, because we use ten digits, 0 through 9. l Hexadecimal is base 16. How many digits do we need to express numbers in hex ? 16 (0 through ?) l A B C D E F

CMSC The Hexadecimal Number System (con’t) Binary Decimal Hexadecimal A B C D E F

CMSC The Hexadecimal Number System (con’t) Example of a hexadecimal number and the values of the positions: 3 C 8 B

CMSC Example of Equivalent Numbers Binary: Decimal: Hexadecimal: 50A7 16 Notice how the number of digits gets smaller as the base increases.