|City||Halifax, Nova Scotia|
|Slogan||Today's Best Music!|
|Frequency||100.1 MHz (FM)|
|First air date||November 1, 1977|
|Format||Hot adult contemporary|
|HAAT||185.1 meters (607 ft)|
|Callsign meaning||C IOO (One hundred)|
(Bell Media Radio)
|Sister stations||CJCH-FM, CJCH-DT|
CIOO-FM is a Canadian radio station, broadcasting at 100.1 FM in Halifax, Nova Scotia. The station uses the on-air brand name C100. It was owned by Toronto based CHUM Limited until that company's buy-out by CTVglobemedia in 2007, and then Bell Media in 2011. CIOO's studios are located at the intersection of Russell and Agricola Streets in Halifax (right behind TV sister CJCH), with its transmitter located on Washmill Lake Drive in Clayton Park.
Based on the current format, C100 competes with CKUL-FM.
In 1976, Radio 920, Ltd., a division of CHUM Limited, applied to the Canadian Radio-television and Telecommunications Commission for a new FM radio station broadcasting at 100,000 watts with a dial position of 100.1 MHz. This would be the third FM radio station in Halifax after FM stations CBC Stereo (CBH-FM) and CHFX-FM. Radio 920, Ltd. also owned CTV affiliate CJCH-TV and CJCH (AM). The CRTC subsequently approved the application.
On November 1, 1977, C100 began broadcasting as an easy listening station. As a new decade approached, C100 changed its programming format to album rock. This gave the listeners an opportunity to hear more than just the top 40 hits from a particular artist, such as other songs not yet on AM radio. In 1983, CHUM Limited tested a simulcast project. A new TV station, ASN, had aired in the province. Together with C100, they would air Atlantic Canada's Choice - a radio/TV program, hosted by Geoff Banks, counting down the week's best albums from 20 to 1. This lasted until spring 1985, where the station again reformatted its programming.
The spring of 1985 saw the station take on another programming angle, Top 40 along with oldies, such as the Beach Boys among others. This format was phased out not long after, when the station moved towards AC. The station ran such slogans as "Lite Rock...Less Talk", "Great Light Rock Hits" and "...Even More Lite Rock Hits". CIOO moved to its current Hot AC format in 1993. Like most Hot AC stations in Canada, C100 leans rhythmic, though not as heavy as sister station CHUM-FM/Toronto. With sister station CJCH-FM adopting a Rhythmic/Dance Top 40 presentation by 2013, CIOO has modified its playlist towards a conventional Adult Top 40 direction.
- The Breakfast Club is the weekday morning program on C100. The show airs from 6:30am – 10:00am, having extended from its old hours of 6:00am–9:00am. It was originally hosted by Kelly Latremouille, Peter Harrison and Moya Farrell until mid-2007. Kelly had debuted with the station in the summer of 1993, replacing John Biggs, who took Kelly's position with 92 CJCH AM at that time. After Kelly Latremouille's departure in late June 2007, Adam Marriott became an interim host along with Harrison and Farrell. On August 17, 2008, Brad Dryden joined the Breaskfast Club as Kelly's replacement. In August 2015, JC Douglas became Brad's replacement on the Show. In January 2017, Melody Rose became Farrell's replacement after she retired from the station after 35 years.
Long before the Breakfast Club, the station used one DJ personality. Geoff Banks hosted the morning show for the better part of the 1980s, before John Biggs took over and shortly thereafter forming the show they have today.
- The Top 9 at 9 is a countdown of the day's most requested songs. It is heard each weekday morning and weeknight at 9 o'clock. When this show first aired in 1993, it was the Top 7 at 7. Currently, it has moved back to the latter name.
- Retro Request Sunday with Nicolle, heard every Sunday morning from 8am to noon, focuses on music from the 1980s. When the 80's boom started its resurgence in 1995, C100 ran the program from 8:00am–10:00am on Saturday mornings. This time slot lasted for around 8 years, with the format sometimes running from 8:00 till noon.
- The Atlantic Canada Countdown with Matt & Deb is C100's weekly countdown of the most popular music of the week in Atlantic Canada. It is heard Sunday mornings from 8 to 10 AM.
C100 formerly broadcast the radio version of the MuchMoreMusic countdown, but stopped airing it sometime in 2007.
- The C100 Summer Cruiser is a mobile prize machine team who broadcast their secret location around the Halifax Regional Municipality multiple times throughout the day all summer. Prizes vary every summer but in the past have included free concert tickets, movie passes, museum passes, gift certificates, C100 'gear' and a chance to fill out a ballot to win a weekly prize or 1 grand prize. A recent addition to the prize rotation are C100 window stickers. Although no official contest regarding the stickers has been announced, there is growing speculation that it will be something quite worthwhile.
C100 brands itself as playing the most music for Halifax  with:
- 100 Minutes of Commercial Free Music airs weekdays 9:00am – 10:40am.
- 60 Minutes of Commercial Free Drive Home airs weekdays 4:00pm – 5:00pm.
- 40 Minutes of Commercial Free Music airs every hour, every day.
Every Year on New Year's Eve, C100 plays the top 100 songs of the radio stations of that year. Past top 5's have been:
- 5- Hinder- "Better Than Me"
- 4- Nelly Furtado- "Do It"
- 3- Plain White T's- "Hey There Delilah"
- 2- Daughtry- "Home"
- 1- OneRepublic ft. Timbaland- "Apologize"
- 5- Daughtry- "Feels Like Tonight"
- 4- Flo Rida ft. T-Pain- "Low"
- 3- Hedley- "Never Too Late"
- 2- Leona Lewis- "Bleeding Love"
- 1- Katy Perry- "I Kissed a Girl"
- 5- Beyoncé- "Halo"
- 4- Taylor Swift- "You Belong with Me"
- 3- Lady Gaga- "Paparazzi"
- 2- Kelly Clarkson- "Already Gone"
- 1- The Black Eyed Peas- "I Gotta Feeling"
- 5- Timbaland ft. Katy Perry- "If We Ever Meet Again"
- 4- Hedley- "Perfect"
- 3- Lady Antebellum- "Need You Now"
- 2- Adam Lambert- "Whataya Want from Me"
- 1- Train- "Hey, Soul Sister"
- 5- Alyssa Reid- "Alone Again"
- 4- Bruno Mars- "Grenade"
- 3- P!nk- "Because You're Perfect"
- 2- Bruno Mars- "Just The Way You Are"
- 1- P!nk- "Raise Your Glass"
- 5- Fun- "We Are Young"
- 4- Maroon 5- "Payphone"
- 3- Train- "Drive By"
- 2- Kelly Clarkson- "Stronger (What Doesn't Kill You)"
- 1- Carly Rae Jepsen- "Call Me Maybe"
- 5- Miley Cyrus- "Wrecking Ball"
- 4- The Lumineers- "Ho Hey"
- 3- P!nk ft. Fun- "Just Give Me A Reason"
- 2- Robin Thicke ft. T.I. and Pharrell Williams- "Blurred Lines"
- 1- Justin Timberlake- "Mirrors"
- 5- John Legend- "All of Me"
- 4- Meghan Trainor- "All About That Bass"
- 3- Pharrell Williams- "Happy"
- 2- Sam Smith- "Stay with Me"
- 1- Taylor Swift- "Shake It Off"
- 5- Omi- "Cheerleader"
- 4- Adele- "Hello"
- 3- The Weeknd- "Can't Feel My Face"
- 2- Ed Sheeran- "Thinking Out Loud"
- 1- Mark Ronson ft. Bruno Mars- "Uptown Funk"
- CIOO-FM history – Canadian Communications Foundation
- Query the REC's Canadian station database for CIOO-FM