1957 – Report 8th grade Geert Groote School

Having moved from The Hague to Amsterdam, visited the Geert Groote School, then located at the Hygeaplein behind the Olympiaplein for 3 months (April, May, June).After summer changed to 2nd grade Gymnasium at Amsterdams Lyceum.

Posted in Nostalgia

August 29 1967 – Our wedding

Posted in Uncategorized

August 1966, one of my first software programs.

A page, (nr 3 of 13) from a program to show computer instructions on the machine level, a socalled “trace” program. Was written for the IBM 360 Model 2, which was never released.
On the left the symbolic machine code, on the right the machine code in hexadecimal (handcoded, since there was no compiler/assembler available yet).

Posted in Nostalgia

Two ways too show the current year in a webpage

A simple example in PHP:

<span><? echo date('Y') ?></span>

Note: PHP has to be integrated with a webserver.

A slightly less simple example in JavaScript:

function currentYear() {
  y = new Date();
  document.getElementById("year").innerHTML = y.getFullYear();
<body onload="currentYear()">
<span id="year"></span>

Should work with any JS supporting browser

Posted in Webpages Tagged , ,

MD5 digest in OORexx

usemd5.rex – a sample MD5 calculation with md5.cls below

parse arg ifn   -- get input filename
input_stream = .stream~new(ifn)
message_digest = .md5~new
do while input_stream~chars>0
  -- calculate digest in chunks of 256 bytes
say message_digest~digest
::requires "md5.cls"

md5.cls – a MD5 implementation in OORexx

-- requires OORexx 4.2.0 or later
-- standard numeric digits of 9 is not enough in this case
::options digits 20
-- Implementation mainly based on pseudocode in https://en.wikipedia.org/wiki/MD5
::class md5 public
::method init
  expose a0 b0 c0 d0 count buffer index K. s  -- instance variables
  use strict arg chunk=""
  -- Initialize message digest
  a0 = .int32~new('67452301'x,"C")   -- A
  b0 = .int32~new('efcdab89'x,"C")   -- B
  c0 = .int32~new('98badcfe'x,"C")   -- C
  d0 = .int32~new('10325476'x,"C")   -- D
  -- The 512 bit chunk buffer
  buffer = .mutablebuffer~new('00'x~copies(64),64)
  -- The position in the buffer to insert new input
  index = 1
  -- message bytecount 
  count = 0 
  -- initialize leftrotate amounts
  nrs = .array~of(7,12,17,22)
  s = nrs~union(nrs)~union(nrs)~union(nrs)
  nrs = .array~of(5,9,14,20)
  s = s~union(nrs)~union(nrs)~union(nrs)~union(nrs)
  nrs = .array~of(4,11,16,23)
  s = s~union(nrs)~union(nrs)~union(nrs)~union(nrs)
  nrs = .array~of(6,10,15,21)
  s = s~union(nrs)~union(nrs)~union(nrs)~union(nrs)
  -- initialize sinus derived constants.
  -- sin function from RXMath Library shipped with OORexx
  -- see ::routine directive at the end of the code 
  do i=0 to 63
    K.i = .int32~new(((2**32)*(sin(i+1,16,R)~abs))~floor) 
  -- process initial string if any
::method update
  expose a0 b0 c0 d0 count buffer index K. s  -- instance variables
  use strict arg chunk
  count += chunk~length
  if chunk~length<65-index then do
    index += chunk~length
  else do
    split = 65-index+1
    parse var chunk part =(split) chunk
    index = 65
  -- Only proces completely filled buffer
  do while index=65
    A = a0
    B = b0
    C = c0
    D = d0
    do i=0 to 63
        when i<16 then do
          F = D~xor(B~and(C~xor(D)))
          g = i
        when i<32 then do
          F = C~xor(D~and(B~xor(C)))
          g = (5*i+1)//16
        when i<48 then do
          F = B~xor(C)~xor(D)
          g = (3*i+5)//16
        otherwise do
          F = C~xor(B~or(D~not))
          g = (7*i)//16
      M = .int32~new(buffer~substr(g*4+1,4)~reverse,"C")  -- 32bit word in little-endian
      dTemp = D
      D = C
      C = B
      B = (B + (A+F+K.i+M)~bitrotate(s[i+1]))
      A = dTemp
    a0 = a0+A
    b0 = b0+B
    c0 = c0+C
    d0 = d0+D
    parse var chunk part 65 chunk
    index = part~length+1
::method digest
  expose a0 b0 c0 d0 count buffer index K s -- instance variables
  padlen = 64
  if index<57 then padlen = 57-index
  if index>57 then padlen = 121-index
  padding = '00'x~copies(padlen)~bitor('80'x)
  bitcount = count*8//2**64
  lowword = bitcount//2**32
  hiword = bitcount%2**32
  lowcount = lowword~d2c(4)~reverse -- make it little-endian
  hicount = hiword~d2c(4)~reverse   -- make it little-endian
  self~update(padding || lowcount || hicount)
return a0~string || b0~string || c0~string || d0~string
-- A convenience class to encapsulate operations on non OORexx-like
-- things such as little-endian 32-bit words  
::class int32 private
::attribute arch class
::method init class
  self~arch = "little-endian"   -- can be adapted for multiple architectures 
-- Method to create an int32 like object
-- Input can be a OORexx whole number (type="I") or
-- a character string of 4 bytes (type="C")
-- input truncated or padded to 32-bit word/string
::method init
  expose char4 int32
  use strict arg input, type="Integer"
  -- type must be one of "I"nteger or "C"haracter
  t = type~subchar(1)~upper
    when t=='I' then do
      char4 = input~d2c(4)
      int32 = char4~c2d
    when t=='C' then do
      char4 = input~right(4,'00'x)
      int32 = char4~c2d
    otherwise do
      raise syntax 93.915 array("IC",type)
::method xor  -- wrapper for OORexx bitxor method
  expose char4
  use strict arg other
return .int32~new(char4~bitxor(other~char),"C")
::method and  -- wrapper for OORexx bitand method
  expose char4
  use strict arg other
return .int32~new(char4~bitand(other~char),"C")
::method or   -- wrapper for OORexx bitor method
  expose char4
  use strict arg other
return .int32~new(char4~bitor(other~char),"C")
::method not   -- OORexx not implementation
  expose char4
return .int32~new(char4~bitxor('ffffffff'x),"C")
::method bitleft -- OORexx shift (<<) implementation
  expose char4 
  use strict arg bits
  bstring = char4~c2x~x2b 
  bstring = bstring~substr(bits+1)~left(bstring~length,'0') 
return .int32~new(bstring~b2x~x2d) 
::method bitright -- OORexx shift (>>) implementation
  expose char4
  use strict arg bits, signed=.false
  bstring = char4~c2x~x2b
  fill = '0'
  if signed then fill = bstring~subchar(1)
  bstring = bstring~left(bstring~length-bits)~right(bstring~length,fill)
return .int32~new(bstring~b2x~x2d)
::method bitrotate  -- OORexx (left) rotate method
  expose char4
  use strict arg bits, direction='left'
  d = direction~subchar(1)~upper
  if d=='L' then do
    leftpart = self~bitleft(bits)
    rightpart = self~bitright(32-bits)
  else do
    leftpart = self~bitleft(32-bits)
    rightpart = self~bitright(bits)
return rightpart~or(leftpart)
::method int  -- retrieve integer as number
  expose int32
return int32
::method char -- retrieve integer as characters
  expose char4
return char4
::method string -- retrieve integer as hexadecimal string
  expose char4
return char4~reverse~c2x~lower
::method '+'  -- OORexx method to add 2 .int32 instances
  expose int32
  use strict arg other
return .int32~new(int32+other~int)
-- Simplify function names for the necessary 'RxMath' functions	
::routine sin EXTERNAL "LIBRARY rxmath RxCalcSin"

Posted in (oo)REXX Tagged