page_title: History of personal computers
section_title: TRS-80
hierarchical_section_title: History of personal computers / 1977 and the emergence of the "Trinity" / TRS-80
caption_attribution_description: English: Tandy Corporation (Radio Shack) TRS-80 Model I computer system
context_page_description: The history of the personal computer as a mass-market consumer electronic device began with the microcomputer revolution of the 1970s. A personal computer is one intended for interactive individual use, as opposed to a mainframe computer where the end user's requests are filtered through operating staff, or a time-sharing system in which one large processor is shared by many individuals. After the development of the microprocessor, individual personal computers were low enough in cost that they eventually became affordable consumer goods. Early personal computers – generally called microcomputers – were sold often in electronic kit form and in limited numbers, and were of interest mostly to hobbyists and technicians.
context_section_description: Tandy Corporation (Radio Shack) introduced the TRS-80, retroactively known as the Model I as improved models were introduced. The Model I combined the motherboard and keyboard into one unit with a separate monitor and power supply. Although the PET and the Apple II offered certain features that were greatly advanced in comparison, Tandy's 3000+ Radio Shack storefronts ensured that it would have widespread distribution that neither Apple nor Commodore could touch.
  The Model I used a Zilog Z80 processor clocked at 1.77 MHz (the later models were shipped with a Z80A processor). The basic model originally shipped with 4 kB of RAM, and later 16 kB, in the main computer. The expansion unit allowed for RAM expansion for a total of 48K. Its other strong features were its full stroke QWERTY keyboard, small size, well written Microsoft floating-point BASIC and inclusion of a monitor and tape deck for approximately half the cost of the Apple II. Eventually, 5.25 inch floppy drives were made available by Tandy and several third party manufacturers. The expansion unit allowed up to four floppy drives to be connected, provided a slot for the RS-232 option and a parallel port for printers.
  The Model I could not meet FCC regulations on radio interference due to its plastic case and exterior cables. Apple resolved the issue with an interior metallic foil but the solution would not work for Tandy with the Model I. Since the Model II and Model III were already in production Tandy decided to stop manufacturing the Model I. Radio Shack had sold 1.5 million Model I's by the cancellation in 1981.
caption: Nov. 1977: TRS-80 Model I
exif: {"Image ImageWidth": "1334", "Image ImageLength": "2002", "Image BitsPerSample": "[8, 8, 8]", "Image PhotometricInterpretation": "2", "Image Make": "Canon", "Image Model": "Canon DIGITAL IXUS II", "Image Orientation": "Horizontal (normal)", "Image SamplesPerPixel": "3", "Image XResolution": "180", "Image YResolution": "180", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS5 Windows", "Image DateTime": "2013:03:31 18:44:35", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "292", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "1222", "Thumbnail JPEGInterchangeFormatLength": "5721", "EXIF ExposureTime": "1/100", "EXIF FNumber": "14/5", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2009:09:27 13:27:55", "EXIF DateTimeDigitized": "2009:09:27 13:27:55", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "5", "EXIF ShutterSpeedValue": "213/32", "EXIF ApertureValue": "95/32", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "95/32", "EXIF SubjectDistance": "61/100", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, auto mode", "EXIF FocalLength": "173/32", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "1182", "EXIF ExifImageLength": "1462", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "Interoperability RelatedImageWidth": "2048", "Interoperability RelatedImageLength": "1536", "EXIF InteroperabilityOffset": "1072", "EXIF FocalPlaneXResolution": "128000/13", "EXIF FocalPlaneYResolution": "128000/13", "EXIF FocalPlaneResolutionUnit": "2", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "1", "EXIF SceneCaptureType": "Standard"}