transfer functions

summary

A transfer function is used to transfer information between variables of different types.

Many older programming languages refer to these as type conversions, data conversions, or just, conversions.

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transfer functions

This subchapter looks at transfer functions.

A transfer function is used to transfer information between variables of different types.

Many older programming languages refer to these as type conversions, data conversions, or just, conversions.

integer and real transfers

ALGOL entier(E) — ALGOL-60 library function that returns the largest integer not greater than the expression.
BASIC INT(x) — BASIC library function that returns the integer portion of an expression. The result is the largest whole number (integer) that is not greater than the expression.

integer and character/string transfers

BASIC VAL(x) — BASIC library function that returns the integer value of a character string or expression. Note that some versions of VAL will strip out leading blanks..

BASIC CHR$(x) — BASIC library function that returns the single element character string containing the ASCII character equivalent of an integer expression in the range of 0 to 255.
Pascal char(x) — Pascal standard function that returns the CHAR character that matches the position in the collating sequence of an argument x.

BASIC ASC(x) — BASIC library function that returns the decimal ASCII value of a string variable..

JOVIAL

assembly language instructions

Data conversion instructions change data from one format to another.

A sign extension operation takes a small value and sign extends it to a larger storage format (such as byte to word).

A type conversion operation changes data from one format to another (such as signed two’s complement integer into binary coded decimal).

• EXT Sign Extend; Motorola 680x0, Motorola 68300; sign extends a byte (8 bits) in a data register to a word (16 bits) or sign extends a word (16 bits) in a data register to a longword (32 bits); sets or clears flags
• CVT Convert; DEC VAX; converts a signed quantity to a different signed data type, source and destination in register or memory, special rounded versions for certain floating conversions; sets or clears flags
• CVTBW Convert Byte to Word; sign extend
• CVTBL Convert Byte to Long; sign extend
• CVTWB Convert Word to Byte; truncated
• CVTWL Convert Word to Long; sign extend
• CVTLB Convert Long to Byte; truncated
• CVTLW Convert Long to Word; truncated
• CVTBF Convert Byte to Floating; exact
• CVTBD Convert Byte to Double float; exact
• CVTWF Convert Word to Floating; exact
• CVTWD Convert Word to Double float; exact
• CVTLF Convert Long to Floating; rounded
• CVTLD Convert Long to Double float; exact
• CVTFB Convert Floating to Byte; truncated
• CVTDB Convert Double float to Byte; truncated
• CVTFW Convert Floating to Word; truncated
• CVTDW Convert Double float to Word; truncated
• CVTFL Convert Floating to Long; truncated
• CVTRFL Convert Rounded Floating to Long; rounded
• CVTDL Convert Double float to Long; truncated
• CVTRDL Convert Rounded Double float to Long; rounded
• CVTFD Convert Floating to Double float; exact
• CVTDF Convert Double float to Floating; rounded
• CBW Convert Byte to Word; Intel 80x86; sign extends a byte (8 bits) in register AL to create a word (16 bits) in the AX register; does not affect flags
• CWD Convert Word to Doubleword; Intel 80x86; sign extends a word (16 bits) in register AX throughout the DX register to create a doubleword (32 bits); does not affect flags
• CWDE Convert Word to Doubleword Extended; Intel 80386; sign extends a word (16 bits) in register AX to create a doubleword (32 bits) in the EAX register; does not affect flags
• CDQ Convert Doubleword to Quadword; Intel 80386; sign extends a doubleword (32 bits) in register EAX to create a quadword (64 bits) in the EDX register; does not affect flags
• EXTB Sign Extend Byte; Motorola 680x0, Motorola 68300; sign extends a byte (8 bits) in a data register to a longword (32 bits); sets or clears flags
• MOVSX Move with Sign Extension; Intel 80x86; moves data from a register or memory to a register, with a sign extension (conversion to larger binary integer: byte to word, byte to doubleword, or word to doubleword); does not affect flags
• MOVZX Move with Zero Extension; Intel 80x86; moves data from a register or memory to a register, with a zero extension (conversion to larger binary integer: byte to word, byte to doubleword, or word to doubleword); does not affect flags
• MOVZ Move Zero Extended; DEC VAX; converts an unsigned integer to a larger unsigned integer, source and destination in register or memory (MOVZBW Byte to Word, MOVZBL Byte to Long, MOVZWL Word to Long); sets or clears flags
• NUM Convert to Numeric; MIX; converts byte encoded character code (MIX character code) in A-register/X-register pair to numeric data in the A-register (accumulator), does not change sign, overflow possible
• CHAR Convert to Characters; MIX; converts numeric data in the A-register (accumulator) into byte encoded character code (MIX character code) in A-register/X-register pair, does not change signs
• PACK Pack; Motorola 680x0; converts byte encoded numeric data (such as ASCII or EBCDIC characters) into binary coded decimals using an adjustment field (3030ドル for ASCII, $F0F0 for EBCDIC), either from data register to data register or memory location to memory location with predecrement of address pointers; does not modify flags
• UNPK Unpack; Motorola 680x0; converts binary coded decimals into byte encoded numeric data (such as ASCII or EBCDIC characters) using an adjustment field (3030ドル for ASCII, $F0F0 for EBCDIC), either from data register to data register or memory location to memory location with predecrement of address pointers; does not modify flags

See also Data Conversion Instructions in Assembly Language