I have chosen a barcode type for my application. Will all scanner models read it?Given you are using one of the standard linear ("normal") codes like Code EAN/UPC, Code 128 or Code 39 you can safely assume that any recent scanner will be able to read it. Obviously, with 2D barcodes (like PDF 417, QR, Aztec or Datamatrix) you will have to use a dedicated 2D barcode scanner or imager.
With Databar GS1 most recent scanners will read the linear subtypes of Databar (Truncated, Limited, Omnidirectional, Expanded), while the 2D subtypes (Stacked, Expanded Stacked, Omnidirectional Stacked) will require a 2D scanner or imager.
Two tips re. Code 128 and ISBN barcodes: With Code 128 the scanner will almost always expect a checksum with the barcode. If the code will not scan you may have printed it without a checksum. For ISBN scanning, make sure that your scanner has the scanning of Addon codes enabled if you also want to scan the Addon barcode.
Another caveat: Some special barcode types will not work with ordinary barcode scanners. This applies to codes intended to control machinery (e.g. Laetus) as well as to postal barcodes (e.g. Postnet).