| Binary Prefix |
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| CATEGORIES ABOUT BINARY PREFIX | |
| measurement | |
| naming conventions | |
| prefixes | |
| units of information | |
| numeration | |
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In computing, Binary Prefix es can be used to quantify large numbers where powers of two are more useful than powers of ten (such as Computer Memory sizes). Each successive prefix is multiplied by 1024 (210) rather than the 1000 (103) used by the SI Prefix system. Binary prefixes are often written and pronounced identically to the SI prefixes, despite the resulting ambiguity. HISTORY Early computers used one of two addressing methods to access the system memory; binary (base-2) or decimal (base-10). For instance, the IBM 701 (1952) used binary and could address 2,048 36-bit words, while the IBM 702 (1953) used decimal and could address 10,000 7-bit words. One of the most successful early computers was the IBM 1401 . It was introduced in 1959 and by 1961 one out every four electronic stored-program computers was an IBM 1401. It used decimal addressing and could have 1400, 2000, 4000, 8000, 12000 or 16000 characters of 8-bit Core storage.1 These sizes were often abbreviated, borrowing the ''k'' from the SI System Of Prefixes ; a reference to a "4k IBM 1401" meant 4,000 characters of storage (memory).2 By the mid 1960s, binary addressing had become the standard architecture in computer design. The computer system documentation would specify the memory size with an exact number such as 32,768, 65,536 or 131,072 words of storage (all seminal 1964 article on IBM System/360 used 1K to mean 1024.4 Figure 1 gives storage (memory) capacity ranges of the various models in "Capacity 8 bit bytes, 1 K = 1024" This style was used by other computer vendors, the CDC 7600 ''System Description'' (1968) made extensive use of K as 1024.5 Another style was to truncate the last 3 digits and append K. The exact values 32,768, 65,536 and 131,072 would then become 32K, 65K and 131K.6 (If 32,768 were instead rounded off, it would be 33K; if K = 1024 were used, 65,536 would become "64K".) This style was used from about 1965 to 1975. These two styles (K = 1024 and truncation) were used loosely around the same time, sometimes by the same company. (In discussions of binary-addressed memories, the exact size was evident from context.) The HP 21MX real-time computer (1974) denoted 196,608 as 196K and 1,048,576 as 1 M,7 while the HP 3000 business computer (1973) could have 64K, 96K, or 128K bytes of memory. | |||
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