&B

From QB64.org wiki
Jump to: navigation, search

The &B prefix denotes that an integer value is expressed in a binary base 2 format using QB64 only.


Syntax

a& = &B1110110000111111


  • The base 2 numbering system uses binary digit values of 1 or 0, or bits on or bits off in computer register switches or memory.
  • Leading zero values can be omitted as they add nothing to the byte return value.
  • Eight binary digits would represent a one byte value ranging from 0 to 255. Four digit values("nibbles") range from 0 to 15.
  • Decimal values returned can be any signed INTEGER, LONG integer, or _INTEGER64 value so use those type of variables when converting directly as shown in the Syntax. The program "overflow" error limits are listed as:
    • INTEGER: 16 binary digits or a decimal value range from -32,768 to 32,767
    • LONG: 32 binary digits or a decimal value range from -2,147,483,648 to 2,147,483,647
    • _INTEGER64: 64 binary digits or decimal values from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.
  • LONG values can be returned by appending the & or ~%(_UNSIGNED INTEGER) symbols after the binary number.
  • VAL can be used to convert "&B" prefixed string values to decimal.
BITS
  • The MSB is the most significant(largest) bit value and LSB is the least significant bit of a binary or register memory address value. The order in which the bits are read determines the binary or decimal byte value. There are two common ways to read a byte:
  • "Big-endian": MSB is the first bit encountered, decreasing to the LSB as the last bit by position, memory address or time.
  • "Little-endian": LSB is the first bit encountered, increasing to the MSB as the last bit by position, memory address or time.

Offset or Position: 0 1 2 3 4 5 6 7 Example: 11110000 ---------------------------------- -------- Big-Endian Bit On Value: 128 64 32 16 8 4 2 1 240 Little-Endian Bit On Value: 1 2 4 8 16 32 64 128 15

The big-endian method compares exponents of 2 7 down to 2 0 while the little-endian method does the opposite.
BYTES
  • INTEGER values consist of 2 bytes called the HI and LO bytes. Anytime that the number of binary digits is a multiple of 16 (2bytes, 4 bytes, etc.) and the HI byte's MSB is on(1), the value returned will be negative. Even with SINGLE or DOUBLE values!

16 BIT INTEGER OR REGISTER AH (High Byte Bits) AL (Low Byte Bits) BIT: 15 14 13 12 11 10 9 8 | 7 6 5 4 3 2 1 0 ---------------------------------------|-------------------------------------- HEX: 8000 4000 2000 1000 800 400 200 100 | 80 40 20 10 8 4 2 1 | DEC: -32768 16384 8192 4096 2048 1024 512 256 | 128 64 32 16 8 4 2 1

The HI byte's MSB is often called the sign bit! When all 16 of the integer binary bits are on, the decimal return is -1.


Comparing the Base Numbering Systems Decimal (base 10) Binary (base 2) Hexadecimal (base 16) Octal (base 8) 0 0000 0 0 1 0001 1 1 2 0010 2 2 3 0011 3 3 4 0100 4 4 5 0101 5 5 6 0110 6 6 7 0111 7 7 -- maxed 8 1000 8 10 maxed-- 9 1001 9 11 10 1010 A 12 11 1011 B 13 12 1100 C 14 13 1101 D 15 14 1110 E 16 15 ------------- 1111 <--- Match ---> F ---------------- 17 -- max 2 16 10000 10 20 When the Decimal value is 15, the other 2 base systems are all maxed out! The Binary values can be compared to all of the HEX value digit values so it is possible to convert between the two quite easily. To convert a HEX value to Binary just add the 4 binary digits for each HEX digit place so: F A C E &HFACE = 1111 + 1010 + 1100 + 1101 = &B1111101011001101 To convert a Binary value to HEX you just need to divide the number into sections of four digits starting from the right(LSB) end. If one has less than 4 digits on the left end you could add the leading zeros like below: &B101011100010001001 = 0010 1011 1000 1000 1001 hexadecimal = 2 + B + 8 + 8 + 9 = &H2B889 See the Decimal to Binary conversion function that uses HEX$ on the &H page.


Example 1: A Decimal to Binary STRING function that does not return leading zeroes.

PRINT BIN$(255) '1 byte(8 bits) maximum PRINT BIN$(32767) 'integer(2 byte, 15 bits) maximum PRINT BIN$(-32768) 'integer(2 byte, 16 bits) minimum PRINT BIN$(-1) 'all 16 bits on FUNCTION BIN$ (n%) max% = 8 * LEN(n%) ': MSB% = 1 'uncomment for 16 (32 or 64) bit returns FOR i = max% - 1 TO 0 STEP -1 'read as big-endian MSB to LSB IF (n% AND 2 ^ i) THEN MSB% = 1: B$ = B$ + "1" ELSE IF MSB% THEN B$ = B$ + "0" NEXT IF B$ = "" THEN BIN$ = "0" ELSE BIN$ = B$ 'check for empty string END FUNCTION

Code by Ted Weissgerber

11111111 111111111111111 1000000000000000 1111111111111111

Note: The The MSB% flag allows zeroes to be added. Uncomment the MSB% = 1 statement for returns with leading zeroes.


Example 2: QB64 converts the binary values from the example above to INTEGER decimal values automatically.

DEFLNG A-Z a = &B11111111 b = &B111111111111111 c = &B1000000000000000 '& 'or ~% d = &B1111111111111111 '& 'or ~% PRINT a, b, c, d

255 32767 -32768 -1

Bonus example: Add an & symbol after the negative binary numbers to see the LONG decimal values below.

255 32767 32768 65535

Note: The LONG values returned are the same as the values you can get using _UNSIGNED INTEGER (~%).


See also



Navigation:
Go to Keyword Reference - Alphabetical
Go to Keyword Reference - By usage
Go to Main WIKI Page