Throughout the 19th century, the most commonly used forms of screw head (that is, drive types) were simple internal-wrenching straight slots and external-wrenching squares and hexagons. These were easy to machine and served most applications adequately. Rybczynski describes a flurry of patents for alternative drive types in the 1860s through 1890s,but explains that these were patented but not manufactured due to the difficulties and expense of doing so at the time. In 1908, Canadian P. L. Robertson was the first to make the internal-wrenching square socket drive a practical reality by developing just the right design (slight taper angles and overall proportions) to allow the head to be stamped easily but successfully, with the metal cold forming as desired rather than being sheared or displaced in unwanted ways. Practical manufacture of the internal-wrenching hexagon drive (Hex cap screws) shortly followed in 1911. In the early 1930s, the Phillips-head screw was invented by Henry F. Phillips.
Threadform standardization further improved in the late 1940s, when the ISO metric screw thread and the Unified Thread Standard were defined.
Precision screws, for controlling motion rather than fastening, developed around the turn of the 19th century, were one of the central technical advances, along with flat surfaces, that enabled the industrial revolution.They are key components of micrometers and lathes.
Screws and bolts may be made from a wide range of materials, with steel being perhaps the most common, in many 
varieties. Where great resistance to weather or corrosion is required, stainless steel, titanium, brass (steel screws can discolor oak and other woods), bronze, monel or silicon bronze may be used. Galvanic corrosion of dissimilar metals can be prevented (using aluminium screws for double-glazing tracks for example) by a careful choice of material.
Some types of plastic, such as nylon or polytetrafluoroethylene (PTFE), can be threaded and used for fastenings requiring moderate strength and great resistance to corrosion or for the purpose of electrical insulation. Often a surface coating is used to protect the fastening from corrosion (e.g. Bright Zinc Plating for steel screws), to impart a decorative finish (e.g. jappaning) or otherwise alter the properties of the base material. Selection criteria of the screw materials include temperature, required strength, resistance to corrosion, joint material and cost.
Difference
ASME standard B18.2.1 -1996 specifies Hex Cap Screws that range in size from 0.25–3 in (6.35–76.20 mm) in diameter. These fasteners are very similar to hex bolts. They differ mostly in that they are manufactured to tighter tolerances than the corresponding bolts. Machinery's parenthetically to these fasteners as "Finished Hex Bolts".Reasonably, these fasteners might be referred to as bolts but based on the US government document, Distinguishing Bolts from Screws, the US government might classify them as screws because of the tighter tolerance.In 1991 responding to an influx of counterfeit fasteners Congress passed PL 101-592 "Fastener Quality Act".
This resulted in the rewriting of specifications by the ASME B18 committee. B18.2.1was re-written and as a result they eliminated the "Finished Hex Bolts" and renamed them the "Hex Cap Screw"—a term that had existed in common usage long before, but was now also being codified as an official name for the ASME B18 standard.
