Computer Lecture 3
- 1. LECTURE # 3: TRANSFORMING DATA INTO INFORMATION Why computers use the binary number system. Main parts of the CPU and how they work together. The difference between RAM and ROM. Connections that are used to attach devices to a PC.
- 2. HOW COMPUTERS REPRESENT DATA Binary Numbers The Binary Number System Bits and Bytes Text Codes
- 3. BINARY NUMBERS Computer processing is performed by transistors, which are switches with only two possible states: on and off. All computer data is converted to a series of binary numbers– 1 and 0. For example, you see a sentence as a collection of letters, but the computer sees each letter as a collection of 1s and 0s. If a transistor is assigned a value of 1, it is on. If it has a value of 0, it is off. A computer's transistors can be switched on and off millions of times each second.
- 5. THE BINARY NUMBER SYSTEM To convert data into strings of numbers, computers use the binary number system. Humans use the decimal system (“deci”stands for “ten”). The binary number system works the same way as the decimal system, but has only two available symbols (0 and 1) rather than ten (0, 1, 2, 3, 4, 5, 6, 7, 8, and 9). 1010 10 1001 9 1000 8 111 7 110 6 101 5 100 4 11 3 10 2 1 1 0 0 Base 2 Base 10
- 6. BITS AND BYTES A single unit of data is called a bit, having a value of 1 or 0. Computers work with collections of bits, grouping them to represent larger pieces of data, such as letters of the alphabet. Eight bits make up one byte. A byte is the amount of memory needed to store one alphanumeric character. With one byte, the computer can represent one of 256 different symbols or characters.
- 7. 1 0 1 1 0 0 1 0 1 0 0 1 0 0 1 0 1 0 0 1 0 0 1 1 1 1 1 1 1 1 1 1
- 8. WHERE PROCESSING OCCURS Processing takes place in the PC's central processing unit (CPU). The system's memory also plays a crucial role in processing data. Both the CPU and memory are attached to the system's motherboard, which connects all the computer's devices together, enabling them to communicate.
- 10. THE CONTROL UNIT The two main parts of a CPU are the control unit and the arithmetic logic unit (ALU) The control unit directs the flow of data through the CPU, and to and from other devices. The control unit stores the CPU's microcode, which contains the instructions for all the tasks the CPU can perform.
- 12. THE ARITHMETIC LOGIC UNIT The actual manipulation of data takes place in the ALU. The ALU can perform arithmetic and logic operations. The ALU is connected to a set of registers—small memory areas in the CPU, which hold data and program instructions while they are being processed.
- 13. THE ROLE OF MEMORY RAM stores data and program code needed by the CPU. The contents of RAM change rapidly and often. Read-only memory (ROM) is nonvolatile (or permanent). It holds instructions that run the computer when the power is first turned on. The CPU accesses each location in memory by using a unique number, called the memory address.
- 16. CACHE MEMORY Cache memory is high-speed memory that holds the most recent data and instructions that have been loaded by the CPU. Cache is located directly on the CPU or between the CPU and RAM, making it faster than normal RAM. CPU-resident cache is called Level-1 (L1) cache. External cache is called Level-2 (L2) cache. The amount of cache memory has a tremendous impact on the computer's speed.