In digital logic, a don't-care term is an input-sequence (a series of bits) to a function that the designer does not care about, usually because that input would never happen, or because differences in that input would not result in any changes to the output. By considering these don't-care inputs, designers can potentially minimize their function much more so than if the don't-care inputs were taken to have an output of all 0 or all 1. Examples of don't-care terms are the binary values 1010 through 1111 (10 through 15 in decimal) for a function that takes a BCD value, because a BCD value never takes on values from 1010 to 1111. Don't-care terms are important to consider in minimizing, using Karnaugh maps and the Quine–McCluskey algorithm.

"Don't care" may also refer to an unknown value in a multi-valued logic system, in which case it may also be called an X value. In the Verilog hardware description language such values are denoted by the letter "X". In the VHDL hardware description language such values are denoted (in the standard logic package) by the letter "X" (forced unknown) or the letter "W" (weak unknown).

Samuel Timothy "Tim" McGraw (born May 1, 1967) is an American country singer and actor. Many of McGraw's albums and singles have topped the country music charts with total album sales in excess of 40 million units in the US, making him the eighth best-selling artist, and the third best-selling country singer, in the Soundscan era. He is married to country singer Faith Hill and is the son of former baseball player Tug McGraw.

McGraw had 11 consecutive albums debut at Number One on the Billboard albums charts. Twenty-one singles hit No. 1 on the Billboard Hot Country Songs chart. He has won 3 Grammys, 14 Academy of Country Music awards, 11 Country Music Association (CMA) awards, 10 American Music Awards, and 3 People's Choice Awards. His Soul2Soul II Tour with Faith Hill is the highest grossing tour in country music history, and one of the top five among all genres of music.

McGraw has ventured into acting, with supporting roles in The Blind Side (with Sandra Bullock), Friday Night Lights, The Kingdom, and Four Christmases (with Vince Vaughn and Reese Witherspoon), and lead roles in Flicka (2006) and Country Strong (2010). He was a minority owner of the Arena Football League's Nashville Kats. Taylor Swift's debut single, "Tim McGraw", refers to him and his song, "Can't Tell Me Nothin'".

Taylor Alison Swift (born December 13, 1989) is an American singer-songwriter and occasional actress. Raised in Wyomissing, Pennsylvania, Swift moved to Nashville, Tennessee at the age of fourteen to pursue a career in country music. She signed to the independent label Big Machine Records and became the youngest songwriter ever hired by the Sony/ATV Music publishing house. The release of Swift's self-titled debut album in 2006 established her as a country music star. "Our Song", her third single, made her the youngest sole writer and singer of a number one song on the country chart. She received a Best New Artist nomination at the 50th Grammy Awards.

Swift's second album, Fearless, was released in late 2008. Buoyed by the chart success of the singles "Love Story" and "You Belong with Me", Fearless attracted a crossover audience and became the top-selling album of 2009. The record won four Grammy Awards, with Swift becoming the youngest ever Album of the Year winner. Fearless also received Album of the Year plaudits at the American Music Awards, Academy of Country Music Awards and Country Music Association Awards, making it the most awarded album in country music history. In 2010, Swift released her third album, Speak Now, which sold over one million copies in its first week. She then embarked on the 111-date Speak Now World Tour, which was attended by over 1.6 million fans and has become one of the highest-grossing concert tours of all time. The album's third single, "Mean", won two Grammy Awards for Best Country Song and Best Country Solo Performance. Swift is currently recording her fourth studio album, due for release in the fall of 2012.

Keith Lionel Urban (born 26 October 1967) is a Australian country music singer, songwriter and guitarist whose commercial success has been mainly in the United States and Australia. Urban was born in New Zealand and began his career in Australia at an early age. In 1991, he released a self-titled debut album, and charted four singles in Australia before moving to the United States in 1992. Eventually, Urban found work as a session guitarist before starting a band known as The Ranch, which recorded one studio album on Capitol Records and charted two singles on the Billboard country charts.

Still signed to Capitol, he made his solo American debut in 1999 with the album Keith Urban. Certified platinum in the U.S., it also produced his first American Number One in "But for the Grace of God". His breakthrough hit was the Number One "Somebody Like You", from his second Capitol album Golden Road (2002). This album also earned Urban his first Grammy Award win for "You'll Think of Me", its fourth single and the fourth Billboard Number One of his career. 2004's Be Here, his third American album, produced three more Number Ones, and became his highest-selling album, earning 4× Multi-Platinum certification. Love, Pain & the Whole Crazy Thing was released in 2006, producing the record-setting No.17 country chart debut of "Once in a Lifetime", as well as Urban's second Grammy for the song "Stupid Boy", while a Greatest Hits package entitled Greatest Hits: 18 Kids followed in late 2007. This album was re-released a year later as Greatest Hits: 19 Kids with one track added: the number one "You Look Good in My Shirt", which he had previously recorded on Golden Road. Additional albums Defying Gravity and Get Closer were released on 31 March 2009 and 16 November 2010, respectively.

Michael Robert "Mike" Posner (born February 12, 1988) is an American singer, songwriter, and producer. Posner released his debut album, 31 Minutes to Takeoff, on August 10, 2010. The album includes the Billboard Hot 100 Top 10 single "Cooler Than Me," his second single, "Please Don't Go," as well as his third single, "Bow Chicka Wow Wow". As of 2012, he is the ambassador of Reebok Classic's RealFlex range.

Posner was born and raised in Southfield, Michigan. His father, a criminal defense attorney, is Jewish, and his mother is Catholic. Posner attended and graduated from Groves High School, where he ran varsity track and cross-country, and went on to attend Duke University. There, Posner went Sigma Nu and graduated in 2010 with a degree in sociology and a certificate in markets and management, with an overall GPA of 3.59.

Manager Daniel Weisman of Elitaste Inc. first heard about Mike Posner in 2008 when Jared Evan manager Saytum passed on some tracks Posner had created for Weisman's then client Wale. Weisman got in touch with Posner and, impressed by songs including "Cooler Than Me", began an informal mentoring relationship with the artist over iChat. The association was made official in early 2009 after Posner's second mixtape, A Matter of Time (the first mixtape being Reflections of a Lost Teen) started attracting industry attention. Working with Don Cannon and DJ Benzi, the mixtape was released from his dorm room at Duke University in March 2009 under the name, "Mike Posner & the Brain Trust," the Brain Trust referring to Posner's supporters. The release was unusual for being distributed for free through iTunes U, a channel designed for educational audio content. Although Posner was not the only artist to take advantage of this loophole, his release was the most organised and high profile, and attracted the largest response, immediately reaching the number one position on the iTunes U chart, thanks to his manager Saytum.