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Definition: 3 C's


The computer performs all processing by "calculating," "comparing" and "copying" the data residing in memory (RAM). Programs and data are read from the computer's storage and written into memory. Programs and data can also be stored anywhere in the world and written into RAM from a network connection.

Data reside in large blocks in storage known as "sectors." After written into RAM, any byte or group of bytes can be accessed by the CPU for calculation and comparison. This interplay between the CPU, memory and storage is how all computing devices process data. See storage vs. memory.

Calculate - Compute Totals and Keep Track
A computer can add, subtract, multiply and divide numbers to compute money amounts and execute myriad mathematical algorithms. The computer's calculating capability also enables software to keep track of its own internal actions. Programmers simply define a counter in their programs and add 1 to the counter every time a certain condition is met.

Compare - Match One Set With Another
The computer can look at two sets of data and determine whether they are equal or which set is higher or lower in value. In the counter example above, comparing determines when the counter has reached its intended goal. Comparing provides the if-then-else logic and is used for searching, analyzing and evaluating data for countless purposes.

Copy - From One Place to Another
The computer can rearrange data for organizing and reporting by copying data from one area in memory to another. In fact, in France and Spain, a computer is actually called an "organizer" because computers do an enormous amount of copying (see ordinateur and computers are copy machines).




It Begins with Software
No processing occurs without first copying the program from storage to memory (RAM). Although interpreted languages remain in source code, instructions in non-interpreted languages have been previously converted into machine language. Because every byte has its own address, each instruction can be independently extracted into the CPU. See byte addressable, machine language, interpreter and ALU.






Compare to Find Things
This example counts California records by writing every record in the database into memory (RAM) until the last record is examined. Each record is written into the same memory space, and if the state field is equal to "CA," a "1" is added to a counter. The blue "CA," the "1" and the counter, initially set to 00000, are defined in the program by the programmer. See buffer.






Copy to Display and Print
Data are stored as contiguous fields in a database but are rendered for humans by copying the characters into the desired order. Dashes are typically not stored as data. They are copied into the required format by the program (see picture).






Compare and Copy to Sort
Resequencing data is accomplished by comparing each item with the others and copying it into the appropriate order. There is also significant calculating going on to keep track of what goes where. Data records are generally indexed, and instead of sorting the actual records, the much smaller indexes are sorted (see index).






Copy and Calculate to Edit
Part of word processing's magic is copying. In this example, in order to insert the "O" from the keyboard, the characters are copied one byte to the right to make room. This illustration is very conceptual, with the actual process requiring many complex calculations of beginning and ending locations.