wjin@cs.purdue.EDU (Woochang Jin) (01/08/90)
What is TENEX mode ? I was trying to ftp some files from simtel. Somebody says that I should be in tenex mode. So I did. What next ? Could anyone explain this ? Thanks, Woochang Jin wjin@cs.purdue.edu
eps@toaster.SFSU.EDU (Eric P. Scott) (01/08/90)
In article <9186@medusa.cs.purdue.edu> wjin@cs.purdue.EDU (Woochang Jin) writes: >What is TENEX mode ? >I was trying to ftp some files from simtel. Somebody says that >I should be in tenex mode. So I did. What next ? >Could anyone explain this ? WSMR-SIMTEL20.ARMY.MIL is a DECSystem-20, and DEC-20s have 36-bit words. SIMTEL20 is best known for its collections of software for 8/16/32-bit machines. So the question is: how does one get 8-bit bytes into 36-bit words? Well, there are two obvious answers: one is, "you cram as many bits as you can in each word, giving you 4 1/2 bytes each." The other is, "you cram as many bytes as you can in each word, and throw the remaining bits away." The former is what the FTP defines as "TYPE I" (IMAGE); it's bitwise-verbatim. The latter is what the FTP defines as "TYPE L 8" (local representation for 8-bit bytes). On 8/16/32- bit machines these are identical. Not so here. User-FTPs typically provide the commands BINARY and TENEX to refer to TYPE I and TYPE L 8 respectively. (TENEX was an operating system developed by BBN, and is the predecessor of TOPS-20, which SIMTEL20 uses.) The answer to your question is, "the DEC-20 has instructions that conveniently manipulate data stored as an integral number of bytes per word, and while it wastes space, it significantly increases machine performance this way." Note that ASCII files are normally stored as 5 7-bit bytes per word, with only one bit in 36 wasted. -=EPS=-