The Macintosh SE was a personal computer

Personal computer

A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

 manufactured by Apple between March 1987 and October 1990. This computer marked a significant improvement on the Macintosh Plus

Macintosh Plus

The Macintosh Plus computer was the third model in the Macintosh line, introduced on January 16, 1986, two years after the original Macintosh and a little more than a year after the Macintosh 512K, with a price tag of US$2599...

 design and was introduced by Apple at the same time as the Macintosh II

Macintosh II

The Apple Macintosh II was the first personal computer model of the Macintosh II series in the Apple Macintosh line and the first Macintosh to support a color display.- History :...

.
It had a similar case to the original Macintosh

Macintosh 128K

The Macintosh 128K machine, released as the "Apple Macintosh", was the original Apple Macintosh personal computer. Its beige case contained a monitor and came with a keyboard and mouse. An indentation in the top of the case made it easier for the computer to be lifted and carried. It had a selling...

 computer, but with slight differences in color and styling.
The SE's notable new features, compared to its similar predecessor the Macintosh Plus

Macintosh Plus

The Macintosh Plus computer was the third model in the Macintosh line, introduced on January 16, 1986, two years after the original Macintosh and a little more than a year after the Macintosh 512K, with a price tag of US$2599...

, were:

• First compact Macintosh
  Compact Macintosh
  "Compact Macintosh" or "Classic Macintosh" are informal terms that refer to the direct descendants of the original Macintosh personal computer case design by Apple Computer, Inc. All of them are all-in-one desktop computer designs with the display integrated in the computer case, but not the...
  
   with an internal drive bay
  Drive bay
  A drive bay is a standard-sized area for adding hardware to a computer. Most drive bays are fixed to the inside of a case, but some can be removed....
  
   for a hard disk (originally 20 MB or 40 MB) or a second floppy drive.
• First compact Macintosh that featured an expansion slot (SE stood for "System Expansion").
• Used the Apple Desktop Bus
  Apple Desktop Bus
  Apple Desktop Bus is an obsolete bit-serial computer bus connecting low-speed devices to computers. Used primarily on the Macintosh platform, ADB equipment is still available but not supported by most Apple hardware manufactured since 1999....
  
   (ADB), introduced with the Apple IIGS
  Apple IIGS
  The Apple , the fifth and most powerful model in the Apple II series of personal computers produced by Apple Computer. The "GS" in the name stands for Graphics and Sound, referring to its enhanced graphics and sound capabilities, both of which greatly surpassed previous models of the line...
  
  , for keyboard and mouse interface.
• Improved SCSI
  SCSI
  Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
  
   support with faster data throughput.
• Better reliability and longer life expectancy due to the addition of a cooling fan.

The SE was designed to accommodate either one or two floppy drives, or a floppy drive and a hard drive.