TOPIC 7—COMPUTER DATA TYPES AND FORMATS

frequency stability. Figure 4-41 is an example of a timing circuit (block and timing diagram) using an oscillator and flip-flop combination. Notice how with the use of a ring counter (flip-flops), we can generate additional phases that can be used for more complex functions involving multiple operations. CAUTION REMEMBER, COMPUTER CIR- CUITS CONTAIN ESDS DEVICES. ONLY PERSONNEL WITH ESDS TRAINING SHOULD HANDLE ESDS DEVICES! TOPIC 7—COMPUTER DATA TYPES AND FORMATS Different types or kinds of data can be processed by a computer. The types are as follows: Bit —The smallest data element or operand is the bit. Individual bits are used primarily in status indicating and flag registers. The two possible states (0 or 1) indicate either ON/OFF, TRUE/FALSE, or other two-state conditions. Depending on the type of computer, single bits in a memory word can be addressable by a single instruction. Larger computers and some of the newer microcomputers have this capability. Most mainframe computers and some newer microprocessors have machine instructions that allow for single-bit operations (set, clear, or test). If a processor cannot address a single bit, there are software algorithms (small programs) that can combine a number of microinstruction to perform single bit operations. Nibble —The next larger data element or operand is the nibble. A nibble is a 4-bit grouping or half-byte of data. Nibbles are used to store a single binary coded decimal (BCD) digit. Byte —Probably the most commonly accessed data element is the 8-bit byte. Microcomputer memories can use a single byte, two bytes, or more. Bytes form the basis for operand operations. In addition, each 8-bit byte can store a single alphanumeric character in American National Standard Code for Information Interchange (ASCII) format or another coding system. It can also hold a binary number equivalent to 25510. Word —For computers with 16-bit or larger computer words, there are two more data elements. The Figure 4-41.—Example of an oscillator and flip-flop combination: A. Block diagram; B. Timing diagram. 4-24