Microsoft Binary Format

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In computing, Microsoft Binary Format (MBF) was a format for floating point numbers used in Microsoft's BASIC language products including MBASIC, QuickBasic and GW-BASIC.[1]

MBF numbers consist of a sign bit, an eight bit exponent with bias 128, and a 23 or 55 bit significand. The decimal point is located before the assumed bit. The MBF double precision format provided slightly more precison than the IEEE 754 format, but less scale.[2][3]

MBF single-precision format (32 bits):

Exponent Sign Significand
8 bits,
bit 31-24
1 bit,
bit 23
23 bits,
bit 22-0
xxxxxxxx s mmmmmmmmmmmmmmmmmmmmmmm

MBF double-precision format (64 bits):

Exponent Sign Significand
8 bits,
bit 63-56
1 bit,
bit 55
55 bits,
bit 54-0
xxxxxxxx s mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm

By the time Visual Basic was released, the IEEE 754 standard had become widely adopted - for example, it was incorporated into Intel's 387 coprocessor and every x86 processor from the 486 on. Visual Basic uses the IEEE 754 format instead of MBF.

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Further reading[edit]

Notes and references[edit]

  1. ^ "IEEE vs. Microsoft Binary Format; Rounding Issues (Complete)". Microsoft Support. November 21, 2006. Retrieved February 24, 2010. 
  2. ^ "IEEE vs. Microsoft Binary Format; Rounding Issues (Complete)". Microsoft Support. November 21, 2006. Retrieved February 24, 2010. 
  3. ^ "Need to access MBF (Microsoft Binary Format) data". Experts Exchange. December 11, 2001. Retrieved February 24, 2010. (subscription required)