Logo can pass extra information to its words, and return information.
The procedure (word) is instructed to expect something and give that something a name.
The colon is used for this purpose.
It passes the information by value and the colon is pronounced as the value of.
When the procedure is run with a command such as CHAIR  200, the word :thesize takes the value 200 so when FD :thesize is executed, the interpreter understands FD, the value of 200.

EDALL ;(to enter the editor mode, then the actual procedure)
TO CHAIR :thesize
REPEAT 4 [FD :thesize RT 90]
FD :thesize
END
CS
REPEAT 9 [CHAIR 50 RT 20 CHAIR 100 WAIT 50 RT 20]
Logo can pass extra information to its words, and return information. The procedure (word) is instructed to expect something and give that something a name. The colon is used for this purpose. It passes the information by value and the colon is pronounced as the value of. When the procedure is run with a command such as CHAIR  200, the word :thesize takes the value 200 so when FD :thesize is executed, the interpreter understands FD, the value of 200.
EDALL ;(to enter the editor mode, then the actual procedure)
TO CHAIR :thesize
REPEAT 4 [FD :thesize RT 90]
FD :thesize
END
CS
REPEAT 9 [CHAIR 50 RT 20 CHAIR 100 WAIT 50 RT 20]
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