title: PL/1 fixed and float, dec and bin data types. Difference between dec and bin. How many bytes?
body: <p>I came from c++ and java and now I am reading book about PL/1 and have some problems with understanding data types.
  First is fixed bin. As I understand actually there are 4 fixed bin types. They are:</p>
  
  <p>fixed bin(7,n)   -- 1 byte</p>
  
  <p>fixed bin(15,n)  -- 2 byte</p>
  
  <p>fixed bin(31,n)  -- 4 byte</p>
  
  <p>fixed bin(63,n)  -- 8 byte</p>
  
  <p>If I write in my program for example fixed bin(10,n) it will be "converted" into fixed bin(15,n) cause PC/mainfraim can hold numbers only in whole bytes.
  As I know there are also fixed dec(m,n) data types. But what is these "magical m numbers" for fixed dec of 1,2,4,8 bytes? Is internally representation in memory of fixed bin and fixed dec equal or different?</p>
  
  <p>And about float.
  What are magical float bin and float dec m numbers? For how many bytes they are? And is internally representation of float bin and float dec equal/different?</p>
  
  <p>I found only float dec(33) (16 bytes i think). And float bin(21) - 4 bytes, (53) - 8 bytes.</p>