Machine data - All data in computers based on digital electronics Boolean data - The Boolean type represents the values: true and false. Numeric data - The integer data types, or "whole numbers" Composite data - Composite types that are derived from more than one primitive type. Enumeration data - This has values which are different from each other, and which can be compared and assigned, but which do not necessarily have any particular concrete representation in the computer's memory String and text data – Any letter of the alphabet

Primary storage - Primary storage (main memory or internal memory), referred to simply as memory, is the only one accessible to the computer. The computer reads instructions stored there and does them as required. Any data that is operated on is also stored there in a basic manner. Secondary storage - Secondary storage (external memory or auxiliary storage) is different from primary storage in that it is not accessible by the computer. The computer usually uses its input or output to access secondary storage and transfers the data using an area in primary storage. Secondary storage does not lose the data when the computer is powered down. It is less expensive than primary storage. Tertiary storage - Tertiary storage or tertiary memory, provides a third level of storage. It involves a robotic mechanism which will insert and dismount removable mass storage media into a storage device according to the system's demands. These data are often copied to secondary storage before use. It is used for storing rarely accessed information since it is much slower than secondary storage. This is useful for large data storage, accessed without humans. Offline storage - Offline storage is a computer data storage on a device that is not under the control of a processing unit. This data is recorded, usually in a secondary or tertiary storage device, and then physically removed or disconnected. It must be inserted or connected by a human before a computer can access it again. Unlike tertiary storage, it cannot be accessed without human interaction.

Simplex mode - data is transmitted in only one direction. Can only send data and cannot receive it or it can only receive data but cannot send data. This method is not popular. Half duplex mode - data can be transmitted in both directions but only in one direction at a time. In this mode, data is sent and received alternatively. It is like a one lane bridge where two way traffic must give way in order to cross the other. Full duplex mode - data can be transmitted in both directions at the same time on the same channel. It is the fastest directional mode of communication. The telephone communication system is an example of full duplex communication mode. Parallel transmission - In parallel transmission, a group data flow at the same time through separate communication lines. It is very fast data transmission. The automobile traffic on a multi-lane highway is an example of parallel transmission. Serial transmission - In serial data transmission, a group of data flow in order through single communication line. The flow of traffic on one-lane residential street is an example of serial data transmission mode. Synchronous transmission – Data is transmitted block by block or word by word at the same time. Each block may contain several bits of data. Data is saved before sending. A large amount of data can be transmitted at a time. The data transmission is very fast. It is most commonly used by remote communication systems. Asynchronous transmission – Data is transmitted one byte at a time. The data is transmitted character by character as the user types it on a keyboard. In this mode, data is not saved before sending.