Editing IBM 305 RAMAC (section)

===Drum memory===
The drum memory was organized into 32 tracks of 100 characters each.

The color code of this table is:

* Yellow &ndash; Storage
* Blue &ndash; Arithmetic
* Green &ndash; Input/output
* Red &ndash; Special function

{| class="wikitable" align="left"
|-
!Track specifier
!Source function
!Destination function
|- BGCOLOR="yellow"
|''W X Y Z''
|colspan=2|General storage
|- BGCOLOR="yellow"
|''0 1 2 3 4 5 6 7 8 9<br>& A B C D E F G H I''
|colspan=2|Instruction storage, general storage
|- BGCOLOR="lightblue"
|''L''
|Read accumulator
|Add to accumulator
|- BGCOLOR="lightblue"
|''M''
|Read & clear accumulator
|Subtract from accumulator
|- BGCOLOR="lightblue"
|''V''
|colspan=2|Multiplicand (1 to 9 characters) or divisor (1 to 9 characters)
|- BGCOLOR="lightblue"
|''N''
| {{N/A}}
|Multiply (1 to 11 characters)<br>Stores 2 to 20 character product<br>in accumulators 0 & 1
|- BGCOLOR="lightblue"
|''P''
| {{N/A}}
|Divide (option)
|- BGCOLOR="lightgreen"
|''K''
|380 Punched card input
| {{N/A}}
|- BGCOLOR="lightgreen"
|''S T''
| {{N/A}}
|323 Punched card output,<br>370 Printer Output,<br>407 Printer output
|- BGCOLOR="lightgreen"
|''Q''
|colspan=2|380 Inquiry input/output
|- BGCOLOR="lightgreen"
|''J''
| {{N/A}}
|350 File Address
|- BGCOLOR="lightgreen"
|''R''
|colspan=2|350 File data input/output
|- BGCOLOR="pink"
|''-''
|Core buffer
|Character selector
|- BGCOLOR="lightgreen"
|''$''
|colspan=2|382 Paper tape input/output (option)
|-
|}
{{clear|Left}}
<code>L</code> and <code>M</code> select the same track, containing ten 10-character "[[Accumulator (computing)|Accumulator]]s". As a destination ''L'' specifies addition, ''M'' specifies subtraction. (Numbers in these accumulators were stored in [[ten's complement]] form, with the X bit of the most significant digit storing the sign. The sign of each accumulator was also held in a [[relay]]. However the 305 automatically converted between its standard signed magnitude format and this format without the need for special programming.)

<code>J</code>, <code>''R''</code>, and <code>-</code> do not select tracks on the drum, they specify other sources and destinations.